Metal foreign-matter detection apparatus and method, and wireless charging system

Abstract

The present application relates to a metal foreign-matter detection apparatus and method, and a wireless charging system. The metal foreign-matter detection apparatus comprises: a detection coil set, comprising a plurality of detection coils, which are arranged between a transmitting coil and a receiving coil, and are used for detecting a magnetic flux change of the transmitting coil and generating an induced voltage on the basis of the magnetic flux change; and a detection module, which is connected to a wave generation circuit and the detection coil set, and is configured to determine, on the basis of the induced voltage of the detection coil set, whether there is a metal foreign matter, acquire, when it is determined that there is a metal foreign matter, an impedance angle of the detection module and the detection coil set, and determine the material properties of the metal foreign matter on the basis of whether the impedance angle is positive or negative. The metal foreign-matter detection apparatus in the present application can implement accurate detection and material property recognition of a small metal foreign matter between a transmitting coil and a receiving coil in a wireless charging system, and has relatively high sensitivity.

Description

Metal foreign object detection device, method and wireless charging system Technical Field

[0001] This application relates to the field of wireless charging technology, and in particular to a metal foreign object detection device, method and wireless charging system. Background Technology

[0002] Wireless power transfer technology is a method of energy transfer from the power grid to electrical equipment without direct electrical contact. Compared with traditional contact charging, wireless charging has developed rapidly due to its advantages such as higher reliability and safety, smaller footprint, flexible usage, less susceptibility to external environmental factors, strong interaction with the power grid, and applicability in certain extreme environments and special conditions. Wireless power transfer technology has already been widely adopted in the field of electric vehicles.

[0003] A high-frequency magnetic field exists between the transmitting and receiving coils of a wireless power transmission system. Due to the various complex applications of this system, foreign objects inevitably enter this area. When a metallic foreign object enters this magnetic field region, it will rapidly heat up due to eddy current losses. If it comes into contact with flammable materials at this time, it can easily cause a fire, posing a safety hazard. Furthermore, the presence of a metallic foreign object will affect the transmission power and efficiency of the wireless power transmission system, altering certain parameters of the coupling mechanism and causing the system to malfunction, or even completely shut down in severe cases. Traditional methods for detecting metallic foreign objects can only detect them; they cannot determine the material properties of the foreign object.

[0004] Summary of the Invention

[0005] Therefore, it is necessary to provide a metal foreign object detection device, method, and wireless charging system for identifying the material properties of metal foreign objects.

[0006] In a first aspect, this application provides a metal foreign object detection device for a wireless charging system. The wireless charging system includes a receiving coil, a transmitting coil, and a wave-generating circuit for generating AC signals, wherein the wave-generating circuit is connected to the transmitting coil; the metal foreign object detection device includes:

[0007] A detection coil group, comprising multiple detection coils, is disposed between the transmitting coil and the receiving coil for detecting changes in the magnetic flux of the transmitting coil and generating an induced voltage based on the changes in magnetic flux.

[0008] The detection module is connected to the wave-generating circuit and the detection coil group respectively. It is used to determine whether there is a metallic foreign object based on the induced voltage of the detection coil group, and when it is determined that there is a metallic foreign object, to obtain the impedance angle of the detection module and the detection coil group, and to determine the material properties of the metallic foreign object based on the sign of the impedance angle.

[0009] In one embodiment, the detection module includes:

[0010] Multiple detection circuits, each of which is connected to a detection coil to obtain the induced voltage of the detection coil;

[0011] A control circuit, connected to the plurality of detection circuits and the wave generation circuit respectively, is used to determine whether there is a metallic foreign object based on whether the maximum or minimum value of the induced voltage of the detection coil group changes, and when it is determined that there is a metallic foreign object, to obtain the impedance angle of the detection loop composed of each detection coil and the corresponding detection circuit, and to determine the material properties of the metallic foreign object based on the sign of the impedance angle, wherein the impedance angle is related to the total resistance and total reactance of the detection loop.

[0012] In one embodiment, the control circuit is further configured to obtain the maximum and minimum values ​​of the induced voltage of each of the detection coils, and to determine the presence of a metallic foreign object if any maximum and minimum value exceeds a certain range from the corresponding initial maximum and minimum value; wherein the initial maximum and minimum value is the maximum and minimum induced voltage value when the detection circuit has not established a connection with the wireless charging system.

[0013] In one embodiment, when the presence of a metallic foreign object is determined, the control circuit is further configured to control the transmitting circuit to perform a frequency sweep operation to obtain the secondary resonant frequency of each detection circuit, and to determine the sign of the impedance angle based on a comparison between the secondary resonant frequency and the initial resonant frequency, so as to determine the material properties of the metallic foreign object based on the sign of the impedance angle; wherein, the initial resonant frequency is the resonant frequency of the detection circuit when the detection circuit has not established a connection with the wireless charging system.

[0014] In one embodiment, the control circuit is further configured to determine that the impedance angle is positive when the secondary resonant frequency is less than the initial resonant frequency;

[0015] The control circuit is also used to determine that the impedance angle is negative when the secondary resonant frequency is greater than the initial resonant frequency.

[0016] In one embodiment, the control circuit is further configured to determine, when the impedance angle is positive, that the metallic foreign object is a non-metallic material containing metallic elements;

[0017] The control circuit is also used to determine that the metallic foreign object is a metallic material when the impedance angle is negative.

[0018] In one embodiment, if the presence of a metallic foreign object is determined, the control circuit is further configured to obtain the total impedance of each detection loop in the non-resonant state, the total resistance of each detection loop in the resonant state, and obtain the value of the impedance angle based on the total impedance and the total resistance.

[0019] In one embodiment, each of the detection circuits includes:

[0020] A series resonant unit is connected to the detection coil to obtain the induced voltage of the detection coil;

[0021] A high-pass filter unit, connected to the series resonant unit, is used to filter the induced voltage;

[0022] The voltage comparison unit is connected to the high-pass filter unit and the control circuit respectively, and is used to determine the maximum and minimum values ​​of the filtered induced voltage and send the maximum and minimum values ​​of the induced voltage to the control circuit.

[0023] Secondly, this application also provides a method for detecting metal foreign objects in a wireless charging system, applied to a metal foreign object detection device in a wireless charging system as described in any of the above embodiments, the method comprising:

[0024] The change in magnetic flux of the transmitting coil is detected, and an induced voltage is generated based on the change in magnetic flux;

[0025] The presence of a metallic foreign object is determined based on the induced voltage.

[0026] If the presence of a metallic foreign object is confirmed, obtain the impedance angle of the detection module;

[0027] The material properties of the metallic foreign object are determined based on the sign of the impedance angle.

[0028] In one embodiment, obtaining the impedance angle of the detection module when a metallic foreign object is determined to be present includes:

[0029] Control the wave generation circuit to perform frequency sweep operation;

[0030] Obtain the second resonant frequency of the detection loop composed of each detection coil and the corresponding detection circuit;

[0031] The sign of the impedance angle is determined by comparing the secondary resonant frequency and the initial resonant frequency; the initial resonant frequency is the resonant frequency of the detection circuit when the detection circuit is not connected to the wireless charging system.

[0032] In one embodiment, the step of obtaining the impedance angle of the detection module when the presence of a metallic foreign object is determined further includes:

[0033] Obtain the total impedance of the detection loop composed of each detection coil and the corresponding detection circuit in a non-resonant state;

[0034] Obtain the total resistance of each of the aforementioned detection circuits in the resonant state;

[0035] The value of the impedance angle is obtained based on the total impedance and the total resistance.

[0036] In one embodiment, determining the material properties of the metallic foreign object based on the sign of the impedance angle includes:

[0037] When the impedance angle is positive, the metallic foreign object is determined to be a non-metallic material containing metallic elements;

[0038] When the impedance angle is negative, the metallic foreign object is determined to be a metallic material.

[0039] Thirdly, this application also provides a wireless charging system, including: a transmitting coil, a receiving coil, a wave transmitting circuit, and a metal foreign object detection device as described in any of the above embodiments, wherein...

[0040] The transmitting circuit is connected to the transmitting coil, and the metal foreign object detection device is disposed between the transmitting coil and the receiving coil. The metal foreign object detection device is used to detect whether there is a metal foreign object between the transmitting coil and the receiving coil.

[0041] In the aforementioned metal foreign object detection device, method, and wireless charging system, the metal foreign object detection device includes a detection coil group and a detection module, with the detection coil group comprising multiple detection coils. By placing multiple detection coils between the transmitting coil and the receiving coil, the magnetic flux change in the magnetic field region between the transmitting and receiving coils is detected. The detection module then acquires the change in the induced voltage generated by the multiple detection coils based on this magnetic flux change, thereby determining the presence of a metal foreign object. This allows for accurate detection of metal foreign objects in the magnetic field region between the transmitting and receiving coils. Furthermore, using multiple detection coils to detect the magnetic field region between the transmitting and receiving coils enables accurate detection of small metal foreign objects, increasing the sensitivity of the metal foreign object detection device of this application. Further, when the presence of a metal foreign object is determined, the impedance angle of the detection coil group and the detection module is acquired. The sign of the impedance angle is used to determine the material properties of the metal foreign object, achieving accurate identification of the metal foreign object. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the 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.

[0043] Figure 1 shows a metal foreign object detection device according to an embodiment;

[0044] Figure 2 shows a metal foreign object detection device provided in another embodiment;

[0045] Figure 3 shows the equivalent circuit of the detection loop composed of the detection coil and the detection circuit in one embodiment;

[0046] Figure 4 shows a detection circuit according to an embodiment;

[0047] Figure 5 shows a high-pass filter circuit according to an embodiment;

[0048] Figure 6 illustrates a method for detecting metallic foreign objects according to an embodiment;

[0049] Figure 7 illustrates a specific embodiment of a method for detecting metallic foreign objects.

[0050] Figure 8 shows a wireless charging system according to an embodiment.

[0051] Explanation of reference numerals in the attached figures:

[0052] 10-Metal foreign object detection device, 100-Detection coil group, 110-Detection coil, 200-Detection module, 210-Detection circuit, 211-Series resonant unit, 212-High-pass filter unit, 213-Voltage comparison unit, 220-Control circuit, 300-Transmitting coil, 400-Wave transmission circuit, 500-Receiving coil. Detailed Implementation

[0053] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0054] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0055] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0056] It is understandable that "at least one" refers to one or more, while "multiple" refers to two or more.

[0057] When used herein, the singular forms of “a,” “an,” and “ / the” may also include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0058] A wireless charging system includes a transmitting coil, a receiving coil, and a transmitting circuit for generating AC signals. The transmitting coil is typically laid underground, and the transmitting circuit is connected to it, sending AC signals to the transmitting coil. The receiving coil is mounted on the chassis of an electric vehicle, and the transmitting and receiving coils are coupled together to transmit electrical energy, charging the electric vehicle. When a metallic foreign object enters the magnetic field region between the transmitting and receiving coils, it will cause two problems. First, the object will rapidly heat up due to eddy current losses, which could easily cause a fire if it comes into contact with flammable materials, posing a safety hazard. Second, the presence of the metallic foreign object will affect the transmission power and efficiency of the wireless power transmission system, altering certain parameters of the coupling mechanism and causing the system to malfunction, or in severe cases, completely shut down.

[0059] Based on this, as shown in Figure 1, this application provides a metal foreign object detection device for a wireless charging system, including a detection coil group 100 and a detection module 200. The detection coil group 100 includes multiple detection coils 110, which are disposed between a transmitting coil 300 and a receiving coil (not shown). The detection module 200 is connected to both the transmitting circuit 400 and the detection coil group 100.

[0060] The detection coil 110 can be used to detect changes in the magnetic flux of the transmitting coil 300 and generate an induced voltage based on these changes. The detection module 200 can determine whether there is a metallic foreign object in the wireless charging system based on the induced voltage generated by the detection coil group 100, and if a metallic foreign object is determined to be present, obtain the impedance angle of the detection module 200 and the detection coil group 100, and determine the material properties of the metallic foreign object based on the sign of the impedance angle.

[0061] It is understood that multiple detection coils 110 are arranged between the receiving coil and the transmitting coil 300, forming a circuit with the detection module 200. Changes in the magnetic flux in the magnetic field region between the transmitting coil 300 and the receiving coil, i.e., changes in the magnetic flux passing through the detection coil group 100, will induce an electromotive force (EMF) in each detection coil 110, and the value of this EMF is related to the magnetic flux passing through the detection coil 110. When a metallic foreign object is present in the magnetic field region between the transmitting and receiving coils, due to the eddy current effect of the metal, the metallic foreign object will affect the magnetic flux in the magnetic field region between the transmitting and receiving coils. That is, when the current frequency and amplitude on the transmitting coil are constant, the metallic foreign object will affect the magnetic flux passing through the detection coil 110, thereby causing a change in the value of the induced EMF on the detection coil 110. Therefore, the detection module 200 can determine whether a metallic foreign object exists in the magnetic field region between the transmitting and receiving coils by the change in the induced voltage on the detection coil group 100.

[0062] Furthermore, after determining that a metallic foreign object exists in the magnetic field region between the transmitting coil and the receiving coil, the detection module 200 acquires the impedance angle of the detection module 200 and the detection coil group 100. The impedance angle reflects the phase shift of voltage and current in the detection module. Metallic foreign objects with different material properties have different effects on the current phase; therefore, the material properties of the metallic foreign object can be determined based on the sign of the impedance angle.

[0063] In this embodiment, the metal foreign object detection device for a wireless charging system includes a detection coil group and a detection module. The detection coil group includes multiple detection coils. By placing multiple detection coils between the transmitting coil and the receiving coil, the magnetic flux change in the magnetic field region between the transmitting and receiving coils is detected. The detection module acquires the change in the induced voltage generated by the multiple detection coils based on the magnetic flux change, thereby determining whether a metal foreign object exists. This allows for accurate detection of metal foreign objects in the magnetic field region between the transmitting and receiving coils. Furthermore, using multiple detection coils to detect the magnetic field region between the transmitting and receiving coils can accurately detect small metal foreign objects, increasing the sensitivity of the metal foreign object detection device. Further, when the presence of a metal foreign object is determined, the impedance angle of the detection coil group and the detection module is acquired. The sign of the impedance angle indicates the material properties of the metal foreign object, achieving accurate identification of the metal foreign object.

[0064] In one embodiment, the detection module 200 includes a plurality of detection circuits 210 and a control circuit 220. Each detection circuit 210 is connected to a detection coil 110, and the control circuit 220 is connected to the wave-generating circuit 400 and the plurality of detection circuits 210 respectively.

[0065] The number of detection circuits 210 and detection coils 110 is the same, and each detection circuit 210 and detection coil 110 constitutes a detection loop. The detection circuit 210 can be used to acquire the induced voltage of the corresponding detection coil 110. The control circuit 220 is used to determine whether a metallic foreign object exists based on whether the maximum or minimum value of the induced voltage of the detection coil 110 changes, and, if a metallic foreign object is determined to exist, to acquire the impedance angle of the detection loop formed by each detection coil 110 and the corresponding detection circuit 210, and to determine the material properties of the metallic foreign object based on the sign of the impedance angle. The impedance angle is related to the total resistance and total impedance of the detection loop.

[0066] It is understood that metallic foreign objects can affect the magnetic flux in the magnetic field region between the transmitting and receiving coils, causing a change in the magnetic flux passing through the detection coil, which in turn causes a change in the induced electromotive force (EMF) on the detection coil. Since the induced EMF is constantly changing, to improve the sensitivity and accuracy of the metallic foreign object detection device of this application, the control circuit 220 mainly determines the presence of a metallic foreign object by judging whether the maximum or minimum value of the induced voltage of the detection coil 110 changes. It should be noted that the maximum or minimum induced voltage mentioned here refers to the maximum or minimum induced voltage of the same detection coil 110 within a preset time period, not the maximum or minimum induced voltage of multiple different detection coils.

[0067] Specifically, the control circuit 220 can obtain the maximum and minimum values ​​of the induced voltage of each detection coil 110, and determine the presence of a metallic foreign object if any maximum or minimum value exceeds a certain range from the corresponding initial maximum or minimum value.

[0068] The initial maximum value is the maximum value of the induced voltage when the detection circuit 210 is not connected to the wireless charging system.

[0069] It is understandable that before performing metal foreign object detection, the maximum and minimum induced voltage values ​​detected by each detection circuit 210 can be obtained and used as the initial maximum and minimum values ​​of the detection coil 110 corresponding to that detection circuit 210. According to circuit principles, when the induced voltage sampled by the detection circuit 210 is at its maximum value, the detection circuit should be in a resonant state. During metal foreign object detection, when a metal foreign object is present in the magnetic field region between the transmitting and receiving coils, the detection circuit becomes detuned. At this time, the detection circuit exhibits current attenuation, meaning the maximum and minimum induced voltage values ​​will shift and fall below the initial maximum and minimum values. Therefore, the control circuit 220 can obtain the induced voltage of the corresponding detection coil 110 through each detection circuit 210, determine the maximum and minimum induced voltage values, and compare them with the corresponding initial maximum and minimum values. If the maximum and minimum induced voltage values ​​of any detection coil 110 exceed a certain range from the corresponding initial maximum and minimum values, it is determined that a metal foreign object is present, thus achieving accurate detection of the metal foreign object.

[0070] If a metallic foreign object is confirmed to be present, the control circuit 220 can also control the wave generation circuit 400 to perform a frequency sweep operation to obtain the secondary resonant frequency of each detection loop, and determine the sign of the impedance angle based on the comparison between the secondary resonant frequency and the initial resonant frequency, so as to determine the material properties of the metallic foreign object based on the sign of the impedance angle.

[0071] The initial resonant frequency is the resonant frequency of the detection circuit when the detection circuit is not connected to the wireless charging system. Before detecting metal foreign objects, the maximum and minimum induced voltage values ​​of each detection circuit can be obtained, and the frequency at which the maximum induced voltage value is obtained can be used as the initial resonant frequency.

[0072] It is understandable that when the wireless charging system operates at a high frequency, the transmitting circuit can sweep the frequency at certain intervals. It should be noted that the amplitude of the AC signal supplied to the transmitting coil remains unchanged when the transmitting circuit performs the frequency sweep operation.

[0073] Figure 3 shows the equivalent circuit of a detection loop composed of multiple detection coils and corresponding detection circuits. Here, L1-Ln represent the equivalent inductance of the n detection loops, C1-Cn represent the equivalent capacitance of the n detection loops, RL1-RLn represent the equivalent internal resistance of the n detection loops, and RD1-RDn represent the detection resistance of the n detection loops. The effect of a metallic foreign object on any detection loop is to either increase or decrease the inductance of the detection coil. It can be understood that a metallic foreign object will increase or decrease the value of the equivalent inductance L in the detection loop, but will not affect the values ​​of the equivalent capacitance C and the equivalent internal resistance RL. Based on the resonant frequency... and impedance angle θ = arctan(X / R) (where, (where R is the equivalent reactance and R is the equivalent resistance) It can be seen that increasing the equivalent inductance L will result in a lower resonant frequency and a positive impedance angle, while decreasing the equivalent inductance L will result in a higher resonant frequency and a negative impedance angle.

[0074] For each detection loop, the detection circuit 210 detects the induced voltage of the detection coil 110 at each frequency and sends the induced voltage to the control circuit 220. The control circuit 220 determines the maximum or minimum induced voltage of the detection loop by comparing the induced voltage of the detection coil, and takes the frequency corresponding to the maximum or minimum induced voltage as the secondary resonant frequency of the detection loop. The control circuit 220 can determine the sign of the impedance angle based on the comparison between the secondary resonant frequency and the initial resonant frequency. Specifically, the control circuit 220 can determine that the impedance angle is positive when the secondary resonant frequency is less than the initial resonant frequency, and negative when the secondary resonant frequency is greater than the initial resonant frequency.

[0075] Furthermore, since non-metallic foreign objects such as ferrite increase coil inductance when they are near the circuit, while metallic foreign objects such as copper and iron decrease coil inductance when they are near the circuit, the control circuit 220 can determine that the metallic foreign object is a non-metallic material containing metallic elements when the impedance angle is positive; the control circuit 220 can determine that the metallic foreign object is a metallic material when the impedance angle is negative.

[0076] In this embodiment, the detection module includes multiple detection circuits and a control circuit. Each detection circuit is connected to a detection coil, and the control circuit is connected to the multiple detection circuits and a wave-generating circuit. The detection circuit detects the induced voltage of the corresponding detection coil, and the control circuit determines whether a metallic foreign object exists based on whether the maximum and minimum values ​​of the multiple induced voltages change, thereby achieving accurate detection of the metallic foreign object. Further, when a metallic foreign object is determined to exist, the control circuit controls the wave-generating circuit to perform a frequency sweep operation to obtain the secondary resonant frequency of each detection coil and the corresponding detection circuit, and compares it with the corresponding initial resonant frequency. If the secondary resonant frequency is less than the initial resonant frequency, the impedance angle is determined to be positive, and the metallic foreign object is a non-metallic material containing metallic elements; if the secondary resonant frequency is greater than the initial resonant frequency, the impedance angle is determined to be negative, and the metallic foreign object is a metallic material, thereby achieving the identification of the material properties of the metallic foreign object.

[0077] In one embodiment, if the presence of a metallic foreign object is determined, the control circuit can also obtain the total impedance of each detection loop in the non-resonant state and the total resistance of each detection loop in the resonant state, and obtain the value of the corresponding impedance angle based on the total impedance and the total resistance.

[0078] Please refer to Figure 3 for further explanation. Taking any detection circuit as an example, when a metallic foreign object intrudes, the detection circuit is in a non-resonant state, and its total impedance is:

[0079] Ztotal = Uin / ID

[0080] Wherein, Uin is the voltage value of the AC signal generated by the wave generation circuit, and ID is the current value flowing through one of the detection loops. ID can be obtained by dividing the induced voltage detected by the detection circuit by the detection resistor RD.

[0081] The control circuit controls the transmitting circuit to perform frequency sweeping on the transmitting coil, adjusting the operating frequency of the wireless charging system, and obtaining the current ID1 of the detection circuit in the resonant state. At this time, the circuit exhibits pure resistivity, and the total resistance is:

[0082] Rtotal = Uin / ID1

[0083] The reactance X of the detection circuit at this time can be derived as follows:

[0084] The impedance angle is:

[0085] θ = arctan(|X| / Rtotal)

[0086] Based on this, the control circuit can obtain the impedance angle value of the detection loop composed of each detection coil and the corresponding detection circuit, so as to study the relationship between the material properties of the metallic foreign object and the impedance angle in more depth, and thus more accurately determine the material properties of the metallic foreign object.

[0087] In one embodiment, as shown in FIG4, each detection circuit 210 includes a series resonant unit 211, a high-pass filter unit 212, and a voltage comparison unit 213.

[0088] The series resonant unit 211 is connected to the detection coil 110 and the high-pass filter unit 212, respectively. The voltage comparison unit 212 is connected to the high-pass filter unit 213 and the control circuit 220, respectively. The series resonant unit 211 can acquire the induced voltage of the detection coil 110, and the high-pass filter unit 212 can filter the induced voltage. The circuit structure of the high-pass filter unit 212 can be shown in Figure 5, including a two-stage filter and an operational amplifier. The voltage comparison unit 213 is used to determine the maximum and minimum values ​​of the filtered induced voltage and send these values ​​to the control circuit 220. Through this detection circuit, accurate sampling of the induced voltage of the detection coil 110 can be achieved.

[0089] In one embodiment, this application also provides a method for detecting metal foreign objects in a wireless charging system, which can be applied to the metal foreign object detection device provided in any of the above embodiments. As shown in FIG6, the metal foreign object detection method includes steps S602-S608.

[0090] Step S602: Detect the change in magnetic flux of the transmitting coil and generate an induced voltage based on the change in magnetic flux.

[0091] Multiple detection coils are positioned between the transmitting coil and the receiving coil to detect changes in the magnetic flux of the transmitting coil and generate an induced voltage based on these changes in magnetic flux.

[0092] Step S604: Determine whether there is a metallic foreign object based on the induced voltage.

[0093] The detection module receives the induced voltage from multiple detection coils and determines whether there are metallic foreign objects in the magnetic field region between the transmitting and receiving coils based on the changes in the induced voltage.

[0094] Step S606: If it is determined that there is a metallic foreign object, obtain the impedance angle of the detection module.

[0095] If the presence of a metallic foreign object is confirmed, the detection module calculates its impedance angle.

[0096] Step S608: Determine the material properties of the metallic foreign object based on the sign of the impedance angle.

[0097] The detection module determines the material properties of the metallic foreign object based on the sign of the impedance angle.

[0098] In this embodiment, the detection coil generates an induced voltage based on the change in magnetic flux of the transmitting coil. The presence of a metallic foreign object is determined by the change in the induced voltage, thus realizing the detection of the metallic foreign object. Furthermore, when the presence of a metallic foreign object is determined, the impedance angle of the detection module is obtained, and the material properties of the metallic foreign object are determined based on the sign of the impedance angle, thus realizing the sensitive identification of the metallic foreign object.

[0099] In one embodiment, when a metallic foreign object is determined to be present, obtaining the impedance angle of the detection module includes the steps of controlling the wave transmitting circuit to perform a frequency sweep operation; obtaining the secondary resonant frequency of the detection loop composed of each detection coil and the corresponding detection circuit; and determining the sign of the impedance angle based on a comparison between the secondary resonant frequency and the initial resonant frequency, wherein the initial resonant frequency is the resonant frequency of the detection loop when the detection circuit is not connected to the wireless charging system.

[0100] In one embodiment, when it is determined that a metallic foreign object is present, obtaining the impedance angle of the detection module further includes the steps of obtaining the total impedance of the detection loop composed of each detection coil and the corresponding detection circuit in the non-resonant state; obtaining the total resistance of each detection loop in the resonant state; and obtaining the value of the impedance angle based on the total impedance and the total resistance.

[0101] In one embodiment, determining the material properties of a metallic foreign object based on the sign of the impedance angle includes the steps of determining that the metallic foreign object is a non-metallic material containing metallic elements when the impedance angle is positive, and determining that the metallic foreign object is a metallic material when the impedance angle is negative.

[0102] The steps described above have been explained in detail in the previous introduction of the metal foreign object detection device, and will not be repeated here.

[0103] To better understand, Figure 7 illustrates the usage method of the metal foreign object detection device of this application using a more specific embodiment.

[0104] First, obtain the induced voltage Uref and the resonant frequency fr when the detection loop composed of the detection coil and the detection circuit resonates without metal foreign objects. When detecting metal foreign objects, obtain the maximum value Um of the induced voltage of the detection loop. If |Um - Uref| = 0, it means that the maximum value of the induced voltage has not changed, and there is no metal foreign object in the magnetic field area between the transmitting coil and the detection coil. If |Um - Uref| ≠ 0, it means that there is a metal foreign object in the magnetic field area between the transmitting coil and the detection coil. Further, the control circuit controls the wave - generating circuit to perform a frequency - sweeping operation, and obtain the real - time maximum sampling value Umax, and the corresponding frequency is the secondary resonant frequency fr1. If fr1 < fr, the impedance angle is positive, and the material property of the metal foreign object is a non - metal material containing metal elements; if fr1 > fr, the impedance angle of the detection loop is negative, and the material property of the metal foreign object is a metal material.

[0105] In one embodiment, as shown in FIG. 8. The present application further provides a wireless charging system, including a transmitting coil 300, a receiving coil 500, a wave - generating circuit 400, and the metal foreign object detection device 10 provided in any of the above embodiments. Among them,

[0106] The wave - generating circuit 400 is connected to the transmitting coil 300. The metal foreign object detection device 10 is arranged between the transmitting coil 300 and the receiving coil 500, and the metal foreign object detection device 10 is used to detect whether there is a metal foreign object between the transmitting coil 300 and the receiving coil 500. The wave - generating circuit 400 can be a DDS wave - generating circuit.

[0107] Before the electric vehicle performs wireless charging, first, the metal foreign object detection device 10 detects whether there is a metal foreign object between the transmitting coil 300 and the receiving coil 500. If there is no metal foreign object, the electric vehicle performs wireless charging. The wave - generating circuit 400 provides an alternating - current signal for the transmitting coil 300. Based on the principle of electromagnetic induction, the transmitting coil generates an induced magnetic field. The receiving coil 500 can convert the induced voltage generated by the change of the magnetic flux based on the transmitting coil 300 and flow into the battery of the electric vehicle through an AC - DC converter, a DC - DC converter, etc. to charge the battery.

[0108] Since this wireless charging system adopts a metal foreign object detection device that can accurately detect metal foreign objects, it can timely detect the metal foreign object between the transmitting coil and the receiving coil, avoid the problem that the electric vehicle cannot be normally charged due to the existence of metal foreign objects during charging, reduce the safety hazard during the charging of the electric vehicle, and improve the charging safety.

[0109] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0110] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0111] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A metal foreign object detection device for a wireless charging system, characterized in that, The wireless charging system includes a receiving coil, a transmitting coil, and a wave-generating circuit for generating AC signals, wherein the wave-generating circuit is connected to the transmitting coil. The metal foreign object detection device includes: A detection coil group, comprising multiple detection coils, is disposed between the transmitting coil and the receiving coil for detecting changes in the magnetic flux of the transmitting coil and generating an induced voltage based on the changes in magnetic flux. The detection module is connected to the wave-generating circuit and the detection coil group respectively. It is used to determine whether there is a metallic foreign object based on the induced voltage of the detection coil group, and when it is determined that there is a metallic foreign object, to obtain the impedance angle of the detection module and the detection coil group, and to determine the material properties of the metallic foreign object based on the sign of the impedance angle.

2. The metal foreign object detection device for the wireless charging system according to claim 1, characterized in that, The detection module includes: Multiple detection circuits, each of which is connected to a detection coil to obtain the induced voltage of the detection coil; A control circuit, connected to the plurality of detection circuits and the wave generation circuit respectively, is used to determine whether there is a metallic foreign object based on whether the maximum or minimum value of the induced voltage of the detection coil group changes, and when it is determined that there is a metallic foreign object, to obtain the impedance angle of the detection loop composed of each detection coil and the corresponding detection circuit, and to determine the material properties of the metallic foreign object based on the sign of the impedance angle, wherein the impedance angle is related to the total resistance and total reactance of the detection loop.

3. The metal foreign object detection device for the wireless charging system according to claim 2, characterized in that, The control circuit is also used to obtain the maximum and minimum values ​​of the induced voltage of each detection coil, and to determine the presence of a metallic foreign object if any maximum and minimum value exceeds a certain range from the corresponding initial maximum and minimum value; wherein, the initial maximum and minimum value is the maximum and minimum induced voltage value when the detection circuit has not established a connection with the wireless charging system.

4. The metal foreign object detection device for the wireless charging system according to claim 2, characterized in that, If a metallic foreign object is confirmed to be present, the control circuit is further configured to control the transmitting circuit to perform a frequency sweep operation to obtain the secondary resonant frequency of each detection circuit, and to determine the sign of the impedance angle based on the comparison between the secondary resonant frequency and the initial resonant frequency, so as to determine the material properties of the metallic foreign object based on the sign of the impedance angle; wherein, the initial resonant frequency is the resonant frequency of the detection circuit when the detection circuit has not established a connection with the wireless charging system.

5. The metal foreign object detection device for the wireless charging system according to claim 4, characterized in that, The control circuit is also used to determine that the impedance angle is positive when the secondary resonant frequency is less than the initial resonant frequency; The control circuit is also used to determine that the impedance angle is negative when the secondary resonant frequency is greater than the initial resonant frequency.

6. The metal foreign object detection device for the wireless charging system according to claim 5, characterized in that, The control circuit is also used to determine that the metallic foreign object is a non-metallic material containing metallic elements when the impedance angle is positive. The control circuit is also used to determine that the metallic foreign object is a metallic material when the impedance angle is negative.

7. The metal foreign object detection device for the wireless charging system according to claim 4, characterized in that, If the presence of a metallic foreign object is confirmed, the control circuit is further configured to obtain the total impedance of each detection circuit in the non-resonant state, the total resistance of each detection circuit in the resonant state, and obtain the value of the impedance angle based on the total impedance and the total resistance.

8. The metal foreign object detection device for the wireless charging system according to claim 2, characterized in that, Each of the aforementioned detection circuits includes: A series resonant unit is connected to the detection coil to obtain the induced voltage of the detection coil; A high-pass filter unit, connected to the series resonant unit, is used to filter the induced voltage; The voltage comparison unit is connected to the high-pass filter unit and the control circuit respectively, and is used to determine the maximum and minimum values ​​of the filtered induced voltage and send the maximum and minimum values ​​of the induced voltage to the control circuit.

9. A method for detecting metallic foreign objects in a wireless charging system, characterized in that, The method of the metal foreign object detection device applied to the wireless charging system as described in any one of claims 1-8 includes: The change in magnetic flux of the transmitting coil is detected, and an induced voltage is generated based on the change in magnetic flux; The presence of a metallic foreign object is determined based on the induced voltage. If the presence of a metallic foreign object is confirmed, obtain the impedance angle of the detection module; The material properties of the metallic foreign object are determined based on the sign of the impedance angle.

10. The method for detecting metal foreign objects in a wireless charging system according to claim 9, characterized in that, The step of obtaining the impedance angle of the detection module when the presence of a metallic foreign object is confirmed includes: Control the wave generation circuit to perform frequency sweep operation; Obtain the second resonant frequency of the detection loop composed of each detection coil and the corresponding detection circuit; The sign of the impedance angle is determined by comparing the secondary resonant frequency and the initial resonant frequency; the initial resonant frequency is the resonant frequency of the detection circuit when the detection circuit is not connected to the wireless charging system.

11. The method for detecting metal foreign objects in a wireless charging system according to claim 10, characterized in that, The method of obtaining the impedance angle of the detection module when the presence of a metallic foreign object is determined also includes: Obtain the total impedance of the detection loop composed of each detection coil and the corresponding detection circuit in a non-resonant state; Obtain the total resistance of each of the aforementioned detection circuits in the resonant state; The value of the impedance angle is obtained based on the total impedance and the total resistance.

12. The method for detecting metal foreign objects in a wireless charging system according to claim 11, characterized in that, The determination of the material properties of the metallic foreign object based on the sign of the impedance angle includes: When the impedance angle is positive, the metallic foreign object is determined to be a non-metallic material containing metallic elements; When the impedance angle is negative, the metallic foreign object is determined to be a metallic material.

13. A wireless charging system, characterized in that, include: The transmitting coil, receiving coil, transmitting circuit, and the metal foreign object detection device as described in any one of claims 1-8, wherein, The transmitting circuit is connected to the transmitting coil, and the metal foreign object detection device is disposed between the transmitting coil and the receiving coil. The metal foreign object detection device is used to detect whether there is a metal foreign object between the transmitting coil and the receiving coil.

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