CN113381516A

CN113381516A - Wireless charging foreign matter detection method and device

Info

Publication number: CN113381516A
Application number: CN202010161309.4A
Authority: CN
Inventors: 陈双全; 武志贤
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2020-03-10
Filing date: 2020-03-10
Publication date: 2021-09-10
Also published as: WO2021179784A1

Abstract

The method comprises the steps of determining a first frequency and a second frequency according to an actual resonant frequency of a resonant network, determining difference voltage of the resonant network voltage and preset voltage at the first frequency and the second frequency respectively, comparing an absolute value of the difference of the two difference voltages at two different frequencies with a preset threshold value, and judging whether foreign matters exist or not. The application also provides a foreign matter detection device. By using the foreign matter detection method or device provided by the embodiment of the application, the foreign matter detection precision can be improved, and misjudgment can be reduced.

Description

Wireless charging foreign matter detection method and device

Technical Field

The application relates to the technical field of wireless charging, in particular to a wireless charging foreign matter detection method and device.

Background

In the current wireless charging technology, two technical schemes of a magnetic induction coupling type and a resonant coupling type are most widely applied. The two technical schemes are based on the electromagnetic induction principle, a high-frequency magnetic field is generated through high-frequency alternating current of the transmitting coil, energy is transmitted to the receiving coil from the transmitting coil through the high-frequency magnetic field, and wireless charging is achieved. A typical wireless charging system is composed of a power transmitting device connected to a commercial power and a power receiving device connected to a load. The power transmitting device and the power receiving device are not in electrical contact, and wireless energy transmission is carried out in an electromagnetic induction mode.

An air gap exists between a transmitting coil of a power transmitting device and a receiving coil of a power receiving device of a wireless charging system, and various foreign matters may enter the air gap. When metal foreign matters exist, eddy currents can be generated in metal due to the eddy current effect of the metal in a time-varying magnetic field, so that the metal generates heat, spontaneous combustion (for example, the temperature of tin foil paper is high and can be spontaneously combusted to a certain degree) or other articles are combusted (the metal generates heat to cause the combustion of leaves, paper sheets and the like positioned on the metal), the energy transmission efficiency of a wireless charging system can be reduced, and the metal foreign matters must be detected in order to ensure the safe work and the transmission efficiency of the system.

In the current wireless charging system, foreign object detection is performed by using an induced voltage method. The principle of the induction voltage method is that a detection circuit is placed in a high-frequency magnetic field, whether the magnetic field is distorted or not is judged by judging whether the induction voltage of the detection circuit is abnormal or not, and then whether foreign matters exist or not is judged. The existing wireless charging detection method has insufficient detection precision and is easy to generate misjudgment.

Disclosure of Invention

The application discloses a wireless charging foreign matter detection method and device, which are used for solving the defects that in the prior art, the foreign matter detection method and device are insufficient in precision and prone to generating misjudgment.

In a first aspect of the present application, there is provided a foreign object detection method for a wireless charging system, the method including:

acquiring 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;

calculating a first difference voltage, wherein the first difference voltage is a difference value between the first preset voltage and a first input voltage, and the first preset voltage is an input voltage of the resonant network at the first frequency when no metal foreign matter exists;

calculating a second difference voltage, wherein the second difference voltage is a difference value between the second preset voltage and a second input voltage, and the second preset voltage is an input voltage of the resonant network at the second frequency when no metal foreign matter exists;

calculating a third difference voltage, which is an absolute value of a voltage difference between the first difference voltage and the second difference voltage;

and judging whether foreign matters exist or not according to the third difference voltage.

The foreign matter detection method provided by the first aspect of the application can improve the accuracy of foreign matter detection and reduce misjudgment.

According to the first aspect, in a first possible implementation manner of the first aspect, the determining whether a foreign object exists according to the third difference voltage specifically includes:

and judging whether the third difference voltage is greater than a preset threshold value, and if so, judging that foreign matters exist.

In a first possible implementation manner of the first aspect of the present application, determining the actual resonant frequency of the resonant network may effectively improve the accuracy of foreign object detection.

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

determining the actual resonant frequency of the resonant network, the determining the actual resonant frequency of the resonant network specifically comprising:

measuring an inductance value and a capacitance value of the resonant network, and calculating the actual resonant frequency of the resonant network according to the inductance value and the capacitance value; alternatively, the first and second electrodes may be,

and sweeping the frequency of the resonant network, and measuring that the frequency corresponding to the maximum input voltage of the resonant network is the actual resonant frequency of the resonant network.

In a third possible implementation form of the first aspect, according to the first aspect or the first to the second possible implementation forms of the first aspect, the first frequency is selected in a frequency interval [ (f- Δ f), f ], the second frequency is selected in a frequency interval [ f, (f + Δ f) ], where f is the actual resonance frequency of the resonant network, and Δ f has a value interval [0.01f, 0.5f ].

According to the first aspect or the first to third possible implementation manners of the first aspect, in a fourth possible implementation manner of the first aspect, the resonant network includes N detection coils, and N is an integer greater than or equal to 1.

In a fourth possible implementation manner of the first aspect of the present application, the plurality of detection coils may increase a coverage area for detecting the foreign object.

According to the first aspect or the first to fourth possible implementation manners of the first aspect, in a fifth possible implementation manner of the first aspect, any one of the N detection coils includes a switch, an inductance element, and a capacitance element, the switch is connected in series with the inductance element, and the capacitance element is connected in parallel with the inductance element.

In a second aspect of the present application, a wireless charging foreign object detection method is provided, the method including:

acquiring a first input impedance of the resonant network at a first frequency and a second input impedance of the resonant network 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;

calculating a first differential impedance, which is a difference between the first input impedance and a first preset impedance, wherein the first preset impedance is an input impedance of the resonant network at the first frequency when no metallic foreign matter exists;

calculating a second difference impedance, wherein the second difference impedance is a difference value between the second input impedance and a second preset impedance, and the second preset impedance is an input impedance of the resonant network at the second frequency when no metal foreign matter exists;

calculating a third difference impedance, the third difference impedance being an absolute value of an impedance difference of the first difference impedance and the second difference impedance;

and judging whether foreign matters exist or not according to the third difference impedance.

The foreign object detection method provided by the second aspect of the application can improve the accuracy of foreign object detection and reduce misjudgment.

According to the second aspect, in a first possible implementation manner of the second aspect, the determining whether a foreign object exists according to the third difference impedance specifically includes:

and judging whether the third difference impedance is larger than a preset threshold value or not, and if so, judging that foreign matters exist.

In a first possible implementation manner of the second aspect of the present application, determining the actual resonant frequency of the resonant network may effectively improve the accuracy of foreign object detection.

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

In a third possible implementation form of the second aspect, according to the second aspect or the first to the second possible implementation forms of the second aspect, the first frequency is selected in a frequency interval [ (f- Δ f), f ], the second frequency is selected in a frequency interval [ f, (f + Δ f) ], where f is the actual resonance frequency of the resonant network, and Δ f has a value interval [0.01f, 0.5f ].

According to the second aspect or the first to third possible implementation manners of the second aspect, in a fourth possible implementation manner of the second aspect, the resonant network includes N detection coils, and N is an integer greater than or equal to 1.

In a fourth possible implementation manner of the second aspect of the present application, the plurality of detection coils may increase a coverage area for detecting the foreign object.

In a fifth possible implementation form of the second aspect, the detection coil of the N detection coils includes a switch, an inductance element, and a capacitance element, the switch is connected in series with the inductance element, and the capacitance element is connected in parallel with the inductance element.

In a third aspect of the present application, there is provided a wireless charging foreign object detection apparatus, the apparatus including an ac source, a resonant network, a measurement circuit, and a controller, wherein:

the alternating current source is used for providing alternating current excitation;

the resonance network is used for detecting whether foreign matters exist between the wireless charging transmitting device and the receiving device;

the measuring circuit is used for measuring the input voltage of the resonant network;

the controller is used for determining a first frequency and a second frequency, wherein the first frequency is smaller than the actual resonance frequency of the resonance network, and the second frequency is larger than the actual resonance frequency of the resonance network;

determining a first input voltage of the resonant network at the first frequency and a second input voltage at the second frequency;

calculating a third difference voltage, which is an absolute value of a voltage difference between the first difference voltage and the second difference voltage.

The foreign matter detection device provided by the third aspect of the application can improve the accuracy of foreign matter detection and reduce misjudgment.

According to the third aspect, in a first possible implementation manner of the third aspect, the alternating current source comprises a constant alternating current source. The constant ac source in the first possible implementation manner of the third aspect of the present application may improve the stability of the foreign object detection apparatus.

According to the third aspect or the first possible implementation manner of the third aspect, in a second possible implementation manner of the third aspect, the resonant network includes N detection coils, and N is an integer greater than or equal to 1.

In a second possible implementation manner of the third aspect of the present application, the plurality of detection coils may increase a coverage area for detecting the foreign object.

According to the third aspect or the first to second possible implementation manners of the third aspect, in a third possible implementation manner of the third aspect, each of the N detection coils includes a switch, an inductance element, and a capacitance element, the switch is connected in series with the inductance element, and the capacitance element is connected in parallel with the inductance element.

According to the third aspect or the first to third possible implementation manners of the third aspect, in a fourth possible implementation manner of the third aspect, the measurement circuit is further configured to:

an input impedance of the resonant network is measured.

According to the third aspect or the first to fourth possible implementation manners of the third aspect, in a fifth possible implementation manner of the third aspect, the controller is further configured to:

determining a first frequency and a second frequency, wherein the first frequency is less than the actual resonance frequency of the resonance network, and the second frequency is greater than the actual resonance frequency of the resonance network;

determining a first input impedance of the resonant network at the first frequency and a second input impedance of the resonant network at the second frequency;

and judging whether the third difference impedance is larger than a preset threshold value, and if so, judging that foreign matters exist.

According to the third aspect or the first to fifth possible implementation manners of the third aspect, in a sixth possible implementation manner of the third aspect, the foreign object detection apparatus further includes an alarm configured to:

and when the controller judges that foreign matters exist, alarming is carried out, or a switch for controlling the wireless charging system to work is controlled, and when the controller judges that foreign matters exist, the normal work of the wireless charging system is switched off.

The alarm in the sixth possible implementation manner of the third aspect of the present application can effectively improve the user experience of the foreign object detection device.

In a fourth aspect of the present application, a wireless charging transmitting system is provided, where the wireless charging transmitting system includes a wireless charging foreign object detection device and a wireless charging transmitting device provided in the third aspect, and the wireless charging foreign object detection device is configured to detect whether a foreign object is present in the wireless charging transmitting system.

The wireless transmitting system that charges that this application fourth aspect provided can improve this wireless transmitting system that charges's foreign matter detection's precision, reduces the erroneous judgement.

In a fifth aspect of the present application, a wireless charging receiving system is provided, where the wireless charging receiving system includes the wireless charging foreign object detection device and the wireless charging receiving device provided in the third aspect, and the wireless charging foreign object detection device is configured to detect whether a foreign object is present in the wireless charging receiving system.

The wireless charging receiving system provided by the fifth aspect of the present application can improve the foreign object detection accuracy of the wireless charging receiving system, and reduce misjudgment.

In a sixth aspect of the present application, a wireless charging system is provided, where the wireless charging system includes the wireless charging foreign object detection device and the wireless charging device provided in the third aspect, and the wireless charging foreign object detection device is configured to detect whether a foreign object is present in the wireless charging system.

The wireless charging system provided by the sixth aspect of the present application can improve the accuracy of foreign object detection of the wireless charging system, and reduce erroneous judgment.

By using the foreign matter detection method, device or system, the influence on the foreign matter detection process caused by the induction voltage change of the resonant network caused by the magnetic field change of the transmitting coil, such as the output power, the output voltage, the output current change and the like of the transmitting coil, can be eliminated, so that the foreign matter detection precision is improved, and the misjudgment is reduced.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic diagram of a relationship between impedance and frequency of a detection circuit according to an embodiment of the present disclosure;

fig. 2 is a voltage characteristic curve comparison diagram of a detection circuit for detecting whether an interference induced voltage is superimposed under a condition without a metal foreign object according to an embodiment of the present application;

fig. 3 is a schematic diagram of a wireless charging system according to an embodiment of the present disclosure;

fig. 4 is a schematic structural diagram of a wireless charging system according to an embodiment of the present disclosure;

fig. 5 is a schematic structural diagram of a foreign object detection apparatus according to an embodiment of the present disclosure;

fig. 6 is a schematic diagram of a parallel resonant network according to an embodiment of the present application;

fig. 7 is a comparison graph of input impedance characteristic curves of a resonant network with and without a metallic foreign object according to an embodiment of the present application;

fig. 8 is a schematic flow chart illustrating a foreign object detection method according to an embodiment of the present disclosure;

fig. 9 is a schematic flow chart of another foreign object detection method according to an embodiment of the present application.

Detailed Description

The application is applied to a wireless charging scene. Wireless charging, also known as Wireless Power Transfer (WPT), refers to a technology of converting electric energy into relay energy of other forms (such as electromagnetic field energy, light energy, and microwave energy) by a transmitting device, transmitting the relay energy for a certain distance, and converting the relay energy into electric energy by a receiving device. When wireless charging technology is gradually transformed from a laboratory to a market application, one of the key problems to be solved is the foreign object detection problem.

An air gap exists between a transmitting coil of a power transmitting device and a receiving coil of a power receiving device of a wireless charging system, and various foreign matters may enter the air gap. When metal foreign matters exist, because of the eddy current effect of metal in a time-varying magnetic field, induced eddy current can be formed inside the metal, so that the metal generates heat, and spontaneous combustion (for example, the tin foil paper can be spontaneously combusted when the temperature is high to a certain degree) or other articles are combusted (leaves, paper sheets and the like positioned on the metal generate heat). Meanwhile, since a part of energy is consumed by the metal foreign matter, the energy transmission efficiency of the wireless charging system is also reduced.

Under the high-power wireless scene of charging, for example in the wireless charging system of electric automobile, because the power level of the wireless charging system of electric automobile is high, the overheated risk of foreign matter emergence is big, consequently in order to guarantee the safe work of system and transmission efficiency, need accurately detect the metallic foreign matter, prevent that the calamity from taking place.

Common foreign matter detection methods include primary power coil detection, auxiliary foreign matter detection coils, infrared imaging, temperature detection, acoustic wave detection, magnetic resistance detection, and the like.

A method for detecting metal foreign matters by using a parallel resonance network is characterized in that a detection circuit works under resonance frequency, a constant current source is injected into the parallel resonance network, when no metal foreign matters exist in a wireless charging system, the resonance frequency is omega r, when metal foreign matters exist, the inductance of the detection circuit can be reduced due to the electromagnetic induction effect, and the resonance frequency can be increased. Because the quality factor of the parallel resonant network is high, after a resonant frequency point, an impedance curve is reduced quickly, the change amplitude of the impedance is small, the detection precision is low, in order to improve the detection precision, before the resonant frequency point, a frequency point omega 3dB which is 3dB lower than omega r is taken as a detection point, the impedance characteristic corresponding to the detection circuit is represented by the voltage at two ends of the resonant circuit, when no metal foreign matter exists, the voltage Ueq1 corresponding to the equivalent impedance Zeq1 of the detection circuit at the frequency point omega 3dB is measured in advance and stored in a memory, when the metal foreign matter detection is carried out, the voltage Ueq2 corresponding to the equivalent impedance Zeq2 of the detection circuit at the frequency point omega 3dB is measured, the numerical values of the two voltages Ueq1 and Ueq2 are compared, namely, the numerical value of delta U (3dB) is equal to Ueq1-Ueq2, and if the numerical value of the delta U (3dB) exceeds a set threshold value, the foreign matter is considered to exist. The relationship between the impedance and the frequency of the detection circuit is schematically shown in fig. 1, wherein the solid line represents the case of metal foreign matter, the dotted line represents the case of no metal foreign matter, the horizontal axis represents the frequency, and the vertical axis represents the impedance.

The disadvantage of this solution is that when the wireless charging system is operating, the magnetic field of the transmitting coil will also act on the detection circuit, generating an induced voltage on the detection circuit. Fig. 2 is a graph comparing voltage characteristics of whether or not the disturbance induced voltage is superimposed in the case where no metal foreign matter is present. The interference induced voltage may be an induced voltage of the transmitting coil, when a circuit parameter of the transmitting coil, for example, a change of an output power, an output voltage, and an output current of the transmitting coil may cause an induced voltage Δ Ug, a curve of a voltage Ueq corresponding to an equivalent impedance of the parallel resonant network may be a dotted line, a curve of a voltage Ueq corresponding to an equivalent impedance of the parallel resonant network of the detection circuit that varies with a frequency when the induced voltage Δ Ug of the detection circuit is superimposed with the voltage Ueq corresponding to the equivalent impedance of the parallel resonant network of the detection circuit may be a dotted line, and a value of Δ Ug when Ueq + Δ Ug is detected at a certain frequency point, for example, when the frequency is ω 3dB, exceeds a set threshold, which may be mistaken for a foreign object, thereby generating an erroneous determination. The voltage change of the detection circuit is caused by the circuit parameter change of the transmitting coil, so the voltage change of the detection circuit can be caused by the impedance change of the detection circuit caused by the metal foreign matter, and the induced voltage interference of the magnetic field of the transmitting coil to the detection circuit. Therefore, the existing metal foreign matter detection method does not eliminate the change caused by other factors, such as the change of the output power, the output voltage and the induced voltage of the detection circuit caused by the change of the output current of the transmitting coil, and the detection scheme is easy to generate misjudgment when the working condition is complicated.

The embodiment of the application provides a method, a device and a system for detecting a wireless charging foreign matter based on the principle of an induced voltage method, and is used for solving the problem existing in the prior art when the foreign matter is detected by the induced voltage method.

In order to make the objects, technical solutions and advantages of the present application more clear, the present application will be further described in detail with reference to the accompanying drawings.

The electric automobile is a new energy automobile, and the charging of the electric automobile through a wireless charging system is a technology which is convenient, full-automatic and adaptive to an automatic driving function. Fig. 3 is a schematic diagram of a wireless charging system according to an embodiment of the present disclosure, the wireless charging system including: an electric vehicle 100 and a wireless charging station 101. The electric vehicle 100 may include a wireless charging receiving apparatus 1000, and the wireless charging station 101 may include a wireless charging transmitting apparatus 1010. Currently, the wireless charging system performs a non-contact charging process on the electric vehicle by using the wireless charging receiver 1000 located in the electric vehicle 100 and the wireless charging transmitter 1010 located in the wireless charging station 101 to work together, wherein the wireless charging transmitter 1010 in the wireless charging station 101 is used to transmit ac power to the wireless charging receiver 1000 in the electric vehicle 100, and the wireless charging receiver 1000 in the electric vehicle 100 is used to receive the power transmitted from the wireless charging transmitter 1010 in the wireless charging station 101 and store the power in the battery of the electric vehicle, so as to complete the charging of the electric vehicle.

In one possible implementation, the electric vehicle 100 includes a hybrid 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, and the like. The wireless charging transmitting device 1010 may be disposed on the ground or buried under the ground (fig. 3 shows a case where the wireless charging transmitting device 1010 is buried under the ground), and may wirelessly charge the electric vehicle 100 located above the wireless charging transmitting device 1010. The wireless charging receiving device 1000 may be specifically integrated into the bottom of the electric vehicle 100 or other parts of the vehicle, and when the electric vehicle 100 enters the wireless charging range of the wireless charging transmitting device 1010, the electric vehicle 100 may be charged in a wireless charging manner. The wireless charging transmitter 1010 may also be integrated, i.e., the control circuit and the transmitting coil are integrated, or separated, i.e., the transmitting coil and the control circuit are separated, and the power receiving antenna and the rectifying circuit of the receiver 1000 may be integrated or separated, in which case the rectifying module is usually placed in the vehicle.

Optionally, the non-contact charging may be that the wireless charging receiving device 1000 and the wireless charging transmitting device 1010 perform wireless energy transmission in an electric field or magnetic field coupling manner, specifically, the wireless charging may be in an electric field induction, magnetic resonance, or wireless radiation manner, which is not limited in this application. In a possible implementation manner, the electric vehicle 100 and the wireless charging station 101 can also be charged bidirectionally, and when the wireless charging receiving device 1000 and the wireless charging transmitting device 1010 are both included in the electric vehicle 100 and the wireless charging station 101, the electric vehicle 100 can be charged by the wireless charging station 101 through the power supply, and the electric vehicle 100 can also discharge to the power supply.

Fig. 4 shows a schematic structural diagram of a wireless charging system, which is composed of a transmitting device 201 and a receiving device 202. Fig. 4 (left) shows a schematic structural diagram of a wireless charging transmitting device 201 in a wireless charging station. The wireless charging transmission device 201 includes: the system comprises a power source 2017, a transmission conversion module 2011 connected with the power source 2017, a power transmission antenna 2012, a transmission control module 2013 connected with the transmission conversion module 2011 and the power transmission antenna 2012, a transmission communication module 2014 connected with the transmission control module 2013, an authentication management module 2015 connected with the transmission communication module 2014, and a storage module 2016 connected with the authentication management module 2016.

The emission conversion module 2011 may be connected to the power source 2017, and may be configured to obtain energy from the power source and convert ac or dc power from the power source into high frequency ac power. When the power supply is in alternating current input, the transmitting and converting module consists of a power factor correcting unit and an inverting unit, and the power factor correcting unit can convert 220V power frequency alternating current into direct current; when the power supply is in direct current input, the transmitting and converting module consists of an inverter unit. The power factor correction unit can ensure that the input current phase of the wireless charging system is consistent with the voltage phase of the power grid, reduce the harmonic content of the system and improve the power factor value, so that the pollution of the wireless charging system to the power grid is reduced, and the transmission efficiency and reliability are improved. The power factor correction unit can also increase or decrease the output voltage of the power factor correction unit according to the requirements of the later stage so as to meet the required voltage requirement. The inversion unit can convert the voltage output by the power factor correction unit into high-frequency alternating-current voltage and act on the power transmitting antenna, and the high-frequency alternating-current voltage can greatly improve the transmitting efficiency and the transmission distance. It should be noted that the power source may be a power source inside the wireless charging transmitting system, or may be an external power source external to the wireless charging transmitting system, which is not limited in this application.

The power transmitting antenna 2012 transmits ac power to the receiving antenna in the form of an alternating magnetic field by using the principle of electromagnetic induction in the inductively coupled energy transmission mode, and converts high-frequency ac power into resonant ac power through a network formed by devices mainly including inductors and capacitors in the resonant coupled energy transmission mode, and transmits the resonant ac power to the receiving end coil in the form of an alternating magnetic field.

The transmitting control module 2013 is configured to control parameter adjustment of voltage, current and frequency conversion of the transmitting conversion module 2011 circuit according to a transmitting power requirement of actual wireless charging, and control voltage and current output adjustment of high-frequency alternating current in the power transmitting antenna 2012, and according to different working conditions, namely different coupling coefficients of the transmitting coil and the receiving coil and different receiving end power requirements, the transmitting control module can effectively adjust electrical parameters of the transmitting coil so as to meet different working conditions.

And the transmitting communication module 2014 is used for wireless communication between the wireless charging transmitting device and the wireless charging receiving device, and the communication content comprises power control information, fault protection information, startup and shutdown information, interactive authentication information and the like. On one hand, the wireless charging transmitting device can receive the attribute information, the charging request, the power control information and the mutual authentication information of the electric vehicle, which are sent by the wireless charging receiving device; on the other hand, the wireless charging transmitting device may further transmit wireless charging transmitting control information, mutual authentication information, wireless charging history data information, and the like to the wireless charging receiving device. Specifically, the WIreless Communication manner may include, but is not limited to, any one or a combination of bluetooth (bluetooth), WIreless-broadband (WiFi), Zigbee protocol (Zigbee), Radio Frequency Identification (RFID), Long Range (Lora) WIreless technology, and Near Field Communication (NFC). Furthermore, the transmitting communication module can also communicate with an intelligent terminal of a user belonging to the electric automobile, and the user belonging to the electric automobile realizes remote authentication and user information transmission through a communication function.

The authentication management module 2015 is used for interactive authentication and authority management of the wireless charging transmitting device and the electric vehicle in the wireless charging system, and a processor in the module can process interactive authentication and authority management information and control the transmitting terminal to start a wireless charging function to a receiving terminal which passes authentication and authority.

The storage module 2016 is configured to store charging process data, mutual authentication data (e.g., mutual authentication information), and rights management data (e.g., rights management information) of the wireless charging transmitting device, where the mutual authentication data and the rights management data may be factory settings or self-settings of a user, and the embodiments of the present application do not specifically limit this.

Fig. 4 (right) shows a schematic structural diagram of a wireless charge receiving apparatus 202 in an electric vehicle. The wireless charging receiving apparatus 202 includes: a power receiving antenna 2021, a reception control module 2023 connected to the power receiving antenna, a reception conversion module 2022 connected to the reception control module, and a reception communication module 2024. Optionally, the receiving and converting module may also be connected to the energy storage management module 2026 by being connected to the energy storage management module 2025, and the energy storage management module 2025 may use the energy received by the power receiving antenna 2021 to charge the energy storage module, and further use the energy storage module in the vehicle driving device 2027 of the electric vehicle. It should be noted that the energy storage management module and the energy storage module may be located inside the wireless charging receiving device, or may be located outside the wireless charging receiving device, which is not specifically limited in the embodiment of the present application.

The power reception antenna 2021 is based on the principle of electromagnetic induction in an inductively coupled energy transfer mode or a resonantly coupled energy transfer mode, and is configured to receive energy of an alternating magnetic field from the power transmission antenna and output alternating current.

The receiving control module 2023 is configured to control the voltage, the current, and the frequency conversion parameter of the receiving conversion module according to the receiving power requirement of the actual wireless charging.

The receiving conversion module 2022 is configured to convert the high-frequency current or voltage received by the power receiving antenna into a dc voltage or a dc current required for charging the energy storage module. The receiving conversion module generally consists of a rectifying unit and a direct current conversion unit; the rectification unit converts the high-frequency current and voltage or the high-frequency resonance current and voltage received by the power receiving antenna into direct-current voltage and direct current, and the direct-current conversion unit provides stable direct-current voltage for the post-stage charging circuit to realize constant-mode charging.

The receiving communication module 2024 is used for wireless communication between the wireless charging transmitting device and the wireless charging receiving device. Including power control information, fault protection information, power on/off information, mutual authentication information, etc. On one hand, the wireless charging receiving device can send attribute information, a charging request, power control information and mutual authentication information of the electric vehicle to the wireless charging transmitting device; on the other hand, the wireless charging receiving device may also receive the transmission control information, the mutual authentication information, the wireless charging history data information and the like sent by the wireless charging transmitting device. Specifically, the WIreless Communication mode may include, but is not limited to, any one or a combination of bluetooth (bluetooth), WIreless-broadband (WiFi), Zigbee (Zigbee), Radio Frequency Identification (RFID), Long Range (Lora), and Near Field Communication (NFC). Furthermore, the receiving communication module can also communicate with an intelligent terminal of a user belonging to the electric automobile, the user can realize remote authentication and user information transmission through a communication function, and the intelligent terminal controls the automobile and the transmitting terminal to perform wireless charging interaction.

If a foreign object exists in the wireless charging system, the transmission efficiency of the wireless charging system is reduced due to the fact that the foreign object has an eddy current effect in a magnetic field formed by the transmitting coil.

In order to accurately and efficiently detect the foreign object in the wireless charging system, a first embodiment of the present application provides a foreign object detection device, and as shown in fig. 5, for a structural schematic diagram of the foreign object detection device provided in the embodiment of the present application, the foreign object detection device includes an ac source 301, a resonant network 302, a measurement circuit 303, and a controller 304, and is configured to detect whether a foreign object exists in the wireless charging system. The foreign matter includes metallic foreign matter and non-metallic foreign matter. This foreign matter detection device can be applied to in the wireless scene of charging of electric automobile, also can be applied to in other wireless scenes of charging, for example the wireless scene of charging of unmanned aerial vehicle or the wireless scene of charging of other electronic equipment. The wireless charging foreign matter detection device may be part of the wireless charging transmitting device, i.e. integrated in the wireless charging transmitting device or connected and communicating with the wireless charging transmitting device, or the wireless charging foreign matter detection device may be part of the wireless charging receiving device, i.e. integrated in the wireless charging receiving device or connected and communicating with the wireless charging receiving device, or the wireless charging foreign matter detection device is independent.

The ac source 301 may be a constant current source capable of outputting a constant ac current with a frequency that can be arbitrarily set to provide ac excitation to the resonant network 302, the constant ac current meaning that the current does not vary with the load. In one possible implementation, the frequency of the constant alternating current is set in the range of 10KHz to 10 MHz. The constant alternating current source can improve the stability of the foreign matter detection device.

The resonant network 302 is used to detect whether a foreign object exists between the wireless charging transmitting device and the receiving device. For example, a parallel resonant network circuit. The resonant network 302 includes N equivalent detection coils, N being an integer greater than or equal to 1. Any one of the N detection coils comprises a switch, an inductance element and a capacitance element, wherein the switch is connected with the inductance element in series, and the capacitance element is connected with the inductance element in parallel.

In a possible implementation manner, the resonant network 302 is a resonant network composed of N inductive elements (L1 … Ln) and a capacitive element C1, wherein a resonant circuit formed after each inductive element of the N inductive elements L1 and L2 … Ln is connected to a circuit can be regarded as each equivalent detection coil, that is, there are N detection coils in total, and any one of the N detection coilsThe detection coils each include a switch, an inductance element, and a capacitance element. The plurality of detection coils may increase a coverage area for foreign object detection. The equivalent in the equivalent detection coil is the total equivalent inductance which can be obtained by connecting a plurality of inductance coils in series or in parallel, inductance elements L1 and L2 … Ln in the equivalent detection coil are connected in parallel with a capacitance element C1 to form a parallel resonant network, and inductance elements L1 and L2 … Ln are connected in series with the change-over switches S1 and S2 … Sn. Wherein, each equivalent coil refers to a coil formed by each equivalent inductor and a capacitor C1. In a possible implementation manner, when the foreign object detection is performed, the closing and switching S1 and S2 … Sn are alternately switched, and the foreign object detection is performed on the area covered by the coils including the inductance elements L1 and L2 … Ln of the connected parallel resonant network. For example, as shown in fig. 6, when the switch S1 is closed, the coil including the inductance element L1 is connected in parallel with the capacitance element C1 to form a parallel resonant network, and when resonance occurs, the formula is satisfied

ω is a resonance angular frequency, ω is 2 pi f in relation to the resonance frequency f, L is an inductance value of the inductance element L1, and C is a capacitance value of the capacitance element C1. At this time, the constant alternating current source Is (namely, the alternating current source 301) provides current excitation, so that the metal foreign matter detection can be carried out in the region surrounded by the L1 and the C1. Where C1 can be considered as the equivalent resonant capacitance of the resonant network.

It can be understood that, the structure design of the metal foreign object detection coil (the resonant network 302) has various modes, before the hardware circuit design, finite element simulation of the magnetic field can be performed, by changing the shape, size, connection mode, inductance and the like of different small coils, magnetic field simulation of foreign object detection is performed on various metals with different sizes and different materials, and the scheme with better detection precision is determined as the method for designing the coil. Each equivalent coil of the resonant network may act as a detection coil. Thus, the resonant network 302 can be seen as a detection coil network consisting of a plurality of detection coils. The resonance network adopts a plurality of detection coils in order to cover a larger detectable area, and it can be understood that one detection coil can be adopted, and the specific number and area of the detection coils can be designed according to the actual working condition, which is not limited herein.

In one possible implementation, after simulation and analysis, the actual resonant frequency f of the resonant network 302 is determined to be 300kHz, the equivalent inductance of the detection coil of the access circuit is 100uH, the equivalent capacitance is 2.82nF, and the detection coil is a parallel resonant network. The impedance characteristic curve of the resonant network input impedance Z1 when no metal foreign matter exists can be drawn according to the impedance characteristic of the parallel resonant network, and the impedance characteristic expression of the resonant network input impedance Z1 is shown as formula (1).

ω is the resonance angular frequency, the relation between the resonance angular frequency ω and the resonance frequency f is ω 2 pi f, L is the inductance value of the detection coil formed and closed by the switches in the resonance network, C is the capacitance value of the capacitor C1, and pi is the circumferential ratio.

From the characteristics of the parallel resonant network, the impedance of the parallel resonant network is a maximum at a resonant frequency f of 300 kHz.

When there is a metallic foreign object, the inductance change Δ L of the foreign object detection coil due to electromagnetic induction is usually only about 2%, and the impedance characteristic expression of the resonant network input impedance Z2 in the presence of a metallic foreign object is expressed by expression (2).

Since it is difficult to detect the amount of change in inductance due to the presence of the foreign metal, if it is ensured that the metal can be detected sufficiently small, the detection method can be considered with an inductance change Δ L of 1%, that is, an inductance of 99% L, as shown in fig. 7, which is a graph comparing impedance characteristics of input impedances Z1 and Z2 of the resonant network with and without the presence of the foreign metal.

As can be seen from fig. 7, in the interval less than the resonant frequency f of the resonant network without the metallic foreign object equal to 300kHz, the resonant network input impedance Z1 in the absence of the metallic foreign object is greater than the resonant network input impedance Z2 in the presence of the metallic foreign object; near the resonant frequency point fw of the resonant network in the presence of the metallic foreign matter, the input impedance of the resonant network in the presence of the metallic foreign matter and the input impedance of the resonant network in the absence of the metallic foreign matter can be considered to be approximately the same; the input impedance of the resonant network when a metallic foreign object is present in the section larger than the frequency point fw is larger than the input impedance of the resonant network when no metallic foreign object is present. Further, the farther from the designed resonant frequency point f of the resonant network when no metallic foreign object is present, the smaller the impedance difference of the resonant network between the case where a metallic foreign object is present and the case where no metallic foreign object is present at the same frequency, and therefore, in order to improve the detection accuracy, it is preferable to select the detection point within a certain offset range. It can be seen from the impedance characteristic curve that when the frequency shift exceeds the resonant frequency by 10%, the difference between the input impedance of the resonant network is small and the detection accuracy is low under the condition that the metal foreign object exists and the condition that the metal foreign object does not exist. So the frequency shift range Δ f is assumed to be 10% of the resonant frequency

The measuring circuit 303 is used for measuring the input voltage of the resonant network, the measuring process includes the processes of sampling, filtering, amplifying and the like of the voltage, and the output of the measuring circuit is the voltage proportional to the input voltage of the resonant network. The measuring circuit may be a common voltage measuring circuit or a voltage measuring device.

The controller 304 is configured to process the voltage signal U1 measured by the measurement circuit and an initial voltage signal U2 prestored in the controller when there is no metallic foreign object, perform corresponding calculation, determine whether there is a metallic foreign object according to a comparison between a calculation result and a preset threshold, determine that there is a metallic foreign object if the result is greater than the threshold, and determine that there is no metallic foreign object if the result is not greater than the threshold.

The controller 304 may include therein a filtering unit, a calculating unit, an amplifying unit, and a comparing unit. The filtering unit is used for screening out excitation frequency components of the alternating current source 301; the calculating unit is used for calculating the voltage signal, the amplifying unit is used for amplifying the signal output after calculation to the size easy to distinguish, and the comparing unit is used for comparing the output of the previous stage with the set threshold value and outputting different signals, such as a high-level signal and a low-level signal, according to the comparison result. It should be understood that the internal structure of the controller is not limited, and all devices, modules or units capable of processing the voltage signal and comparing the values of U1 and U2 belong to the controller described in the present application. The controller 304 may further include a memory for storing the initial voltage signal U2 when no metallic foreign object is present. The controller 304 may further comprise a control unit for determining the frequency test points f1 and f2 and sending signals containing the frequency test points f1 and f2 to the ac source 301 for controlling the frequency of the ac power output by the ac source.

In a possible implementation manner, the controller 304 collects the output voltage signal U1 of the resonant network 302 and an initial voltage signal U2 prestored in the controller when no metallic foreign object exists, and uses U1 and U2 as signal sources, and the sizes of U1 and U2 are equal. After a series of filtering, amplifying, adding and other modes, the signal is zero after the subtraction between the U1 and the U2, the controller 304 outputs a signal a indicating that no foreign matter exists in the wireless charging system, and when the voltages U1 and U2 are not equal, the signal is not zero after the subtraction between the U1 and the U2, and the controller 304 outputs a signal B indicating that the foreign matter exists in the wireless charging system. The signals a and B may be digital signals having a significantly recognizable difference or analog signals having a significantly recognizable difference that can be recognized by other parts of the system, e.g., signal a is low or zero and signal B is high. Optionally, a switch for controlling the wireless charging system to operate may be further included, and the normal operation of the wireless charging system is turned off by the identification signal B to prevent an accident; an alarm may also be included for the controller 304 to alarm when it determines that there is a foreign object, and to take different physical actions by recognizing different signals to remind the user to notice the intrusion of the foreign object. When no foreign matter invades, the signal A is recognized by the alarm, and the alarm does not respond. When foreign matter invades, the signal B is recognized by the alarm, and the alarm makes physical reaction, such as the alarm comprising an LED lamp, and the LED lamp flashes; the alarm comprises a buzzer, and the buzzer makes a sound. Thereby prompting the user that the metal foreign body invades.

In another possible implementationIn this way, the controller 304 is configured to determine the actual resonant frequency f of the resonant network; determining frequency test points f1 and f2, wherein f1 is smaller than the actual resonance frequency f of the resonance network, and f2 is larger than the actual resonance frequency f of the resonance network; optionally, f1 and f2 may be both smaller than the actual resonant frequency f of the resonant network, and optionally, f1 and f2 may be both larger than the actual resonant frequency f of the resonant network; determining an input voltage U of the resonant network 302 at a frequency f1_2f1And an input voltage U at a frequency f2_2f2(ii) a Calculating a differential voltage delta U1, wherein the differential voltage delta U1 is a preset voltage U_1f1Input voltage U at frequency f1 with resonant network 302_2f1I.e. Δ U1 ═ U_1f1-U_2f1A predetermined voltage U_1f1The input voltage at frequency f1 of resonant network 302 in the absence of metallic foreign objects; calculating a differential voltage delta U2, wherein the differential voltage delta U2 is a preset voltage U_1f2Input voltage U at frequency f2 with resonant network 302_2f2I.e. Δ U2 ═ U_1f2-U_2f2A predetermined voltage U_1f2The input voltage of the resonant network at the frequency f2 when the resonant network is free of metallic foreign matter; calculating a total difference voltage delta U, wherein the total difference voltage delta U is an absolute value of a voltage difference between the difference voltage delta U1 and the difference voltage delta U2, namely delta U is | delta U1-delta U2 |; and judging whether the delta U is larger than a preset threshold value or not, if so, judging that foreign matters exist, and if not, judging that no foreign matters exist.

In yet another possible implementation, the controller 304 determines the actual resonant frequency f of the resonant network; determining frequency test points f1 and f2, f1 is smaller than the actual resonant frequency f of the resonant network, f2 is larger than the actual resonant frequency f of the resonant network, optionally, f1 and f2 can be both smaller than the actual resonant frequency f of the resonant network, optionally, f1 and f2 can be both larger than the actual resonant frequency f of the resonant network; determining the input impedance L of the resonant network 302 at frequency f1_2f1And an input impedance L at frequency f2_2f2(ii) a Calculating a difference impedance delta L1, wherein the difference impedance delta L1 is a preset impedance L_1f1Input impedance L with the resonant network 302 at frequency f1_2f1I.e., Δ L1 ═ L_1f1-L_2f1A predetermined impedance L_1f1Input impedance of resonant network 302 at frequency f1 for the absence of metallic foreign objects(ii) a Calculating a difference impedance delta L2, wherein the difference impedance delta L2 is a preset impedance L_1f2Input impedance L with the resonant network 302 at frequency f2_2f2I.e., Δ L2 ═ L_1f2-L_2f2A predetermined impedance L_1f2The input impedance of the resonant network at frequency f2 for the absence of metallic foreign matter; calculating total difference impedance delta L, wherein the total difference impedance delta L is the absolute value of the impedance difference between the difference impedance delta L1 and the difference impedance delta L2, namely delta L is | delta L1-delta L2 |; and judging whether the delta L is larger than a preset threshold value or not, if so, judging that foreign matters exist, and if not, judging that no foreign matters exist.

It is understood that, alternatively, the number of frequency test points may be M, where M is an even number greater than or equal to 2, and in a possible implementation, the frequency of 0.5M frequency points is less than the actual resonance frequency of the resonance network, and the frequency of 0.5M frequency points is greater than the actual resonance frequency of the resonance network, and the difference voltage or the difference impedance of the resonance network 302 at each frequency point is determined separately according to the method in the above embodiment, and the total difference impedance is determined, and the total difference impedance is the maximum value of the absolute value of the difference impedance at each frequency point.

In a second embodiment of the present application, a foreign object detection method is provided, as shown in fig. 8, which is a schematic flow chart of the foreign object detection method, and a core flow of the method is as follows:

s401: the actual resonance frequency f of the resonant network is determined. Under the condition of no metal foreign matter, the actual resonance frequency of the resonance network 302 is calculated according to the measured inductance value of each equivalent coil, or the actual resonance frequency f of the resonance network 302 is determined by performing frequency sweeping around the design value of the resonance frequency of the resonance network 302.

In the theoretical design of the resonant network 302, the resonant frequency is determined, but some error exists between the designed value and the actual value due to the device precision of the resonant network. Therefore, in the process of debugging the circuit before actual foreign object detection, it is necessary to first measure the inductance and capacitance of each equivalent coil and calculate the resonant frequency of the resonant network corresponding to each equivalent coil when there is no metal foreign object. The resonant frequency can also be detected in a frequency sweeping mannerThe frequency sweeping means that the frequency of the excitation of the constant-current alternating-current source is changed within a range by changing the frequency of the excitation of the constant-current alternating-current source, the input voltage on the resonant network is measured at the moment, and the frequency of the corresponding constant-current alternating-current source when the input voltage on the resonant network is the maximum is the resonant frequency of the resonant network. Since the deviation of the design value from the actual value is usually not very large, the frequency sweep can usually be performed around the design value of the resonance frequency. For example, the design value of the resonance frequency is f_d300kHz, in the vicinity of the design value of the resonance frequency, e.g., [280kHz, 320kHz]And sweeping the frequency in the frequency interval, wherein the frequency corresponding to the maximum voltage on the resonant network is determined as the resonant frequency in the initial state without the metal foreign matters. Since the detection method of each equivalent coil is the same, the above-mentioned flow is exemplified by one coil, and it is understood that the actual resonant frequency can be determined by the other coils in a similar manner.

S402: and determining a frequency test point. Since the curve descending speeds of the impedance characteristic curves corresponding to different resonant frequencies at the two sides of the resonant frequency point are different, a frequency test point can be respectively determined at the two 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, a frequency point f1 is selected in the [ (f- Δ f), f ] interval, and a frequency point f2 is selected in the [ f, (f + Δ f) ] interval, with (f- Δ f) and (f + Δ f) as boundaries, respectively, and f1 and f2 are used as frequency test points for detecting the metal foreign object. The relationship between the frequency test points f1, 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, f1 and f2 may be both smaller than the actual resonant frequency f of the resonant network, and optionally, f1 and f2 may be both larger than the actual resonant frequency f of the resonant network. The selection standard of the value of Δ f depends on the impedance characteristic curve, the selection principle is that the difference between the impedances when there is a foreign object and when there is no foreign object at the same frequency is obvious, and in a possible implementation manner, the value range of Δ f is [0.01f, 0.5f ]. For example, the impedance difference between the case where there is a foreign object and the case where there is no foreign object is usually large in a range of 0.1f on the left and right of the actual resonance frequency f of the resonance network 302, and the difference becomes small beyond this range, where Δ f is 0.1f, that is, on both sides of the actual resonance frequency f of the resonance network 302, a frequency point f1 is selected in the [ (f-0.1f), f ] section with (f +0.1f) as a boundary, and a frequency point f2 is selected in the [ f, (f +0.1f) ] section, and f1 and f2 are used as frequency test points for detecting a metallic foreign object. For example, when the actual value f of the resonant frequency is 300kHz after the frequency sweep, Δ f is calculated to be 0.1f 30kHz, and on both sides of the actual resonant frequency f of the resonant network 302, f- Δ f-0.1f 270kHz and f + Δ f +0.1f 330kHz are respectively used as boundaries, one frequency point f1 is selected to be 290kHz in the [270kHz, 300kHz ] interval, one frequency point f2 is selected to be 314 in the [300kHz, 300kHz ] interval, and 290kHz and 314kHz are used as the frequency test points for detecting the metallic foreign object.

S403: determining the input voltage U of the resonant network at the frequency point f1 in the absence of metallic foreign bodies_1f1And an input voltage U at a frequency point f2_1f2Will U is_1f1As the preset voltage at the frequency point f1, U_1f2As a preset voltage at the frequency point f 2. In the absence of metallic foreign bodies, the constant current source sends a current excitation at frequency f1, and the measuring circuit detects the input voltage U of the resonant network 302_1f1And the frequency f1 and the input voltage U are compared_1f1To the memory of the controller 304. In the absence of metallic foreign bodies, the constant current source sends a current excitation at frequency f2, and the measuring circuit detects the input voltage U of the resonant network 302_1f2And the frequencies f2 and U are combined_1f2To the memory of the controller 304. For example, in the absence of metallic foreign objects, the constant current source sends a current excitation at a frequency f1 of 290kHz, and the measurement circuit detects the input voltage U of the resonant network 302_1f1And changing the frequency f1 to 290kHz and the input voltage U_1f1To the memory of the controller 304. In the absence of metallic foreign bodies, the constant current source sends a current excitation at a frequency f 2-314 kHz, and the measuring circuit detects the input voltage U of the resonant network 302_1f2And the frequency f2 is 314kHz and U_1f2To the memory of the controller 304.

S404: determining a resonant network 3 at the time of metal foreign object detection02 input voltage U at frequency point f1_2f1And an input voltage U at a frequency point f2_2f2. In the detection of the metal foreign matter, the constant current source sends current excitation with the frequency f1, and the measuring circuit 303 detects the input voltage U of the resonant network 302_2f1And the frequency f1 and the input voltage U are compared_2f1To the memory of the controller 304. In the detection of the metal foreign matter, the constant current source sends current excitation with the frequency f2, and the measuring circuit 303 detects the input voltage U of the resonant network 302_2f2And the frequencies f2 and U are combined_2f2To the memory of the controller 304. For example, in the case of metal foreign object detection, the constant current source sends a current excitation with a frequency f 1-290 kHz, and the measuring circuit 303 detects the input voltage U of the resonant network 302_2f1And changing the frequency f1 to 290kHz and the input voltage U_2f1To the memory of the controller 304. In the detection of the metal foreign matter, the constant current source sends current excitation with the frequency f 2-314 kHz, and the measuring circuit 303 detects the input voltage U of the resonant network 302_2f2And the frequency f2 is 314kHz and U_2f2To the memory of the controller 304.

S405: calculating the preset voltage U of the resonant network 302 at the frequency point f1_1f1And an input voltage U_2f1Δ U1, Δ U1 is the difference voltage at the frequency point f 1. In the controller 304, the input voltage U of the resonant network is compared when the current excitation frequency of the constant current source is f1 when there is no metallic foreign matter_1f1And the input voltage U of the resonant network when the metal foreign matter is detected and the current excitation frequency of the constant current source is f1_2f1Δ U1, Δ U1 ═ U_1f1-U_2f1. When there is no metal foreign matter in the metal foreign matter detection, it is understood that U is theoretically_1f1＝U_2f1，ΔU1＝U_1f1-U_2f10. However, since the system parameters may not be exactly the same, in practice, U is judged_1f1And U_2f1Is less than a threshold, i.e., Δ U1 ═ U_1f1-U_2f1＜U_set1It is considered that no foreign matter is present in the metal foreign matter detection. For example, when f1 is 290kHz, Δ U1 is U when detecting a metal foreign substance_1f1-U_2f1No metal foreign matter is present when detecting metal foreign matterThing, U_1f1And U_2f1Is less than a threshold, Δ U1 ═ U_1f1-U_2f1＜U_set1(ii) a When the metal foreign matter is detected, a metal foreign matter U exists_1f1And U_2f1Is greater than a threshold, Δ U1 ═ U_1f1-U_2f1＞U_set1. Optionally, Δ U1 may also be an input voltage U for calculating the resonant network 302 at the frequency point f1_2f1And a preset voltage U_1f1I.e. Δ U1 ═ U_2f1-U_1f1。

S406: calculating the preset voltage U of the resonant network 302 at the frequency point f2_1f2And an input voltage U_2f2Δ U2, Δ U2 is the difference voltage at the frequency point f 2. In the controller 304, the input voltage U of the resonant network is compared when the current excitation frequency of the constant current source is f2 when there is no metallic foreign matter_1f2And the input voltage U of the resonant network when the metal foreign matter is detected and the current excitation frequency of the constant current source is f2_2f2Δ U2, Δ U2 ═ U_1f2-U_2f2. When there is no metal foreign matter in the metal foreign matter detection, it is understood that U is theoretically_1f2＝U_2f2，ΔU2＝U_1f2-U_2f20. However, since the system parameters may not be exactly the same, in practice, U is judged_1f2And U_2f2Is less than a threshold, i.e., Δ U2 ═ U_1f2-U_2f2＜U_set2It is considered that no foreign matter is present in the metal foreign matter detection. For example, when f1 is 290kHz, Δ U2 is U when detecting a metal foreign substance_1f2-U_2f2When the metal foreign matter is detected, no metal foreign matter, U_1f2And U_2f2Is less than a threshold, Δ U2 ═ U_1f2-U_2f2＜U_set2(ii) a When the metal foreign matter is detected, a metal foreign matter U exists_1f2And U_2f2Is greater than a threshold, Δ U2 ═ U_1f2-U_2f2＞U_set2. Optionally, Δ U2 may also be an input voltage U for calculating the resonant network 302 at the frequency point f2_2f2And a preset voltage U_1f2I.e. Δ U2 ═ U_2f2-U_1f2。

S407: the absolute value Δ U of the voltage difference of the difference voltage at the frequency point f1 and the difference voltage at the frequency point f2 is calculated, Δ U being the total difference voltage. In the controller 304, calculating the absolute value of the voltage difference between the difference voltage at the frequency point f1 and the difference voltage at the frequency point f2 yields the total difference voltage, i.e., Δ U ═ Δ U1- Δ U2 |.

S408: comparing the delta U with a preset threshold value, and judging whether the metal foreign matters exist according to the comparison result. Theoretically, when there is no metallic foreign matter, Δ U ═ Δ U1- Δ U2| ═ 0. When a metal foreign body exists, the induced magnetic field is distorted by the existence of the foreign body, for example, the metal foreign body is also induced with an induced electromotive force in a time-varying magnetic field, the electromotive force generates a closed loop current, namely an eddy current, in the metal foreign body, and the eddy current can generate the magnetic field. Nonmetal foreign matters such as organism foreign matters can also cause the time-varying magnetic field to generate distortion, so the embodiment of the application can also be used for detecting other nonmetal foreign matters. In a possible implementation manner, the eddy magnetic field generated by the metallic foreign object generates 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, as shown in fig. 1, and as can be seen from fig. 1, the impedance of the resonant circuit is different between the two sides of the resonant frequency ω r at ω 1. When the frequency is less than omega 1, the impedance of the detection circuit when the metal foreign matter exists is greater than the impedance of the resonance circuit when the metal foreign matter does not exist; when the frequency is higher than omega 1, the impedance of the resonance circuit when the metal foreign matter exists is smaller than the impedance of the detection circuit when the metal foreign matter does not exist. The difference in impedance affects the difference in voltage. However, the direction and magnitude of the difference between the foreign object induced voltage and the input voltage of the resonant network 302 at different frequencies are different, i.e. Δ U1 is not equal to Δ U2, and Δ U | Δ U1- Δ U2| ≠ 0. It is understood that in practical applications, due to the existence of the error, when the metal foreign matter is not present, Δ U may not be 0. Therefore, in order to increase the detection accuracy, a threshold value U can be preset according to the requirements of specific working conditions and error ranges_set. In the controller 304, the total difference voltage Δ U is compared with a preset threshold of the controller, and when Δ U is larger than the preset threshold rangeI.e. Δ U ═ Δ U1- Δ U2| > U_setThe presence of foreign matter is considered; when the delta U is smaller than a preset threshold range, namely, the delta U is | delta U1-delta U2| < U_setThen, it is considered that no metal foreign matter is present. It can be understood that, in the embodiment of the present application, the method for measuring the voltage difference at two frequencies can effectively improve the detection accuracy and avoid the false detection compared with the method for measuring the voltage difference at one frequency.

As can be seen from fig. 1, under the two different situations of no metal foreign matter and metal foreign matter, because the difference values of the impedance characteristic curves of the resonant network at the two sides of the resonant frequency are different, but the induced voltages generated by the common interference signals can be considered to be approximately equal at different frequencies, the common interference signals under different complex conditions, such as the interference of the magnetic field change of the transmitting coil and the different coupling coefficients caused by the different relative positions between the transmitting coil and the receiving coil, can be effectively eliminated according to the method, the accuracy of detecting the metal foreign matter is improved, the misjudgment is reduced, and the purpose of detecting the high-precision metal foreign matter is achieved.

For example, when detecting a metallic foreign object, there is a disturbance caused by a change in the magnetic field of the transmitting coil, and when there is no metallic foreign object and the current excitation frequency of the constant current source is f1, the input voltage of the resonant network is U_1f1The magnetic field variation of the transmitting coil generates an interference voltage Ui at a current excitation frequency f1 of the constant current source₁Then, when detecting a metal foreign object, the constant current source sends a current excitation with frequency f1, and the input voltage of the resonant network 302 detected by the measuring circuit 303 should be U_2f1+Ui₁. The input voltage of the resonant network is U when no metal foreign matter exists and the current excitation frequency of the constant current source is f2_1f2The magnetic field variation of the transmitting coil generates an interference voltage Ui at a current excitation frequency f2 of the constant current source₂Then, when detecting a metal foreign object, the constant current source sends a current excitation with frequency f2, and the input voltage of the resonant network 302 detected by the measuring circuit 303 should be U_2f2+Ui₂. In the controller 304, the input voltage U of the resonant network is compared when the current excitation frequency of the constant current source is f1 when there is no metallic foreign matter_1f1And the presence of a change in the magnetic field of the transmitting coilAt the current excitation frequency f1 of the constant current source, the input voltage U of the resonant network is used for detecting the metal foreign matter_2f1+Ui₁Δ U1, Δ U1 ═ U_1f1-(U_2f1+Ui₁). Comparing the input voltage U of the resonant network when the metal foreign matter is not present and the current excitation frequency of the constant current source is f2_1f2And in the presence of interference caused by the change in the magnetic field of the transmitting coil, the input voltage U of the resonant network at the time of metal foreign object detection at the current excitation frequency f2 of the constant current source_2f2+Ui₂Δ U2, Δ U2 ═ U_1f2-(U_2f2+Ui₂). In the controller 304, the total difference voltage Δ U ═ Δ U1 to Δ U2|, at the f1 and f2 frequency points is calculated. While the induced voltage due to the variation of the magnetic field of the transmitting coil is equal at different frequencies, i.e. Ui₁＝Ui₂Fig. 2 is a schematic diagram showing the frequency variation of the resonance network input voltage superimposed with the interference induced voltage, where Ueq is the resonance network input voltage, and Ueq + Δ U is the resonance network input voltage superimposed with the interference induced voltage. Therefore, when there is no metal foreign object, theoretically, the total differential voltage Δ U is | Δ U1- Δ U2| 0, and it can be understood that, in practice, the total differential voltage Δ U is smaller than a threshold value, and there is no misjudgment. When the total differential voltage when the foreign matter exists is the same as the total differential voltage when the foreign matter exists without the interference of the induced voltage, the threshold setting can also be the same, and the misjudgment can not be generated.

In the third embodiment of the present application, another foreign object detection method is provided, which is different from the second embodiment in that in the third embodiment, the measurement circuit detects the impedance of the resonant network. When the excitation of the resonant network is an ac current source, the relationship between the voltage of the resonant network and the impedance is U ═ I × Z, and detecting the voltage is the most direct method, and after detecting the impedance of the resonant network, the voltage of the resonant network may be estimated from the measured impedance and the current data of the current source. There are many methods for detecting impedance, such as an impedance detection circuit or an impedance detection device, which are not limited herein. Fig. 9 is a flow chart of the metal foreign matter detection method, which includes the following core flows:

s501: the actual resonance frequency f of the resonant network is determined. Under the condition of no metal foreign matter, the actual resonance frequency of the resonance network 302 is calculated according to the measured inductance value of each equivalent coil, or the actual resonance frequency f of the resonance network 302 is determined by performing frequency sweeping around the design value of the resonance frequency of the resonance network 302.

In the theoretical design of the resonant network 302, the resonant frequency is determined, but some error exists between the designed value and the actual value due to the device precision of the resonant network. Therefore, in the process of debugging the circuit before actual foreign object detection, it is necessary to first measure the inductance and capacitance of each equivalent coil and calculate the resonant frequency of the resonant network corresponding to each equivalent coil when there is no metal foreign object. The resonance frequency detection can also be carried out in a frequency sweeping mode, wherein the frequency sweeping mode refers to that the excitation frequency of the constant-current alternating-current source is changed within a range by changing the excitation frequency of the constant-current alternating-current source, the input voltage on the resonance network is measured at the moment, and the frequency of the corresponding constant-current alternating-current source is the resonance frequency of the resonance network when the input voltage on the resonance network is the maximum. Since the deviation of the design value from the actual value is usually not very large, the frequency sweep can usually be performed around the design value of the resonance frequency. For example, the design value of the resonance frequency is f_d300kHz, in the vicinity of the design value of the resonance frequency, e.g., [280kHz, 320kHz]And sweeping the frequency in the frequency interval, wherein the frequency corresponding to the maximum voltage on the resonant network is determined as the resonant frequency in the initial state without the metal foreign matters. Since the detection method of each equivalent coil is the same, the above-mentioned flow is exemplified by one coil, and it is understood that the actual resonant frequency can be determined by the other coils in a similar manner.

S502: and determining a frequency test point. Since the curve descending speeds of the impedance characteristic curves corresponding to different resonant frequencies at the two sides of the resonant frequency point are different, a frequency test point can be respectively determined at the two 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, a frequency point f1 is selected in the [ (f- Δ f), f ] interval, and a frequency point f2 is selected in the [ f, (f + Δ f) ] interval, with (f- Δ f) and (f + Δ f) as boundaries, respectively, and f1 and f2 are used as frequency test points for detecting the metal foreign object. The relationship between the frequency test points f1, 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, f1 and f2 may be both smaller than the actual resonant frequency f of the resonant network, and optionally, f1 and f2 may be both larger than the actual resonant frequency f of the resonant network. The selection standard of the value of Δ f depends on the impedance characteristic curve, the selection principle is that the difference between the impedances when there is a foreign object and when there is no foreign object at the same frequency is obvious, and in a possible implementation manner, the value range of Δ f is [0.01f, 0.5f ]. For example, the impedance difference between the case where there is a foreign object and the case where there is no foreign object is usually large in a range of 0.1f on the left and right of the actual resonance frequency f of the resonance network 302, and the difference becomes small beyond this range, where Δ f is 0.1f, that is, on both sides of the actual resonance frequency f of the resonance network 302, a frequency point f1 is selected in the [ (f-0.1f), f ] section with (f +0.1f) as a boundary, and a frequency point f2 is selected in the [ f, (f +0.1f) ] section, and f1 and f2 are used as frequency test points for detecting a metallic foreign object. For example, when the actual value f of the resonant frequency is 300kHz after the frequency sweep, Δ f is calculated to be 0.1f 30kHz, and on both sides of the actual resonant frequency f of the resonant network 302, f- Δ f-0.1f 270kHz and f + Δ f +0.1f 330kHz are respectively used as boundaries, one frequency point f1 is selected to be 285kHz in the interval of [270kHz, 300kHz ], one frequency point f2 is selected to be 320kHz in the interval of [300kHz, 330kHz ], and 285kHz and 320kHz are used as frequency test points for detecting the foreign metal object.

S503: determining the input impedance L of the resonant network at frequency point f1 in the absence of metallic foreign bodies_1f1And an input impedance L at the frequency point f2_1f2Is prepared by mixing L_1f1As the preset impedance at the frequency point f1, L is_1f2As a preset impedance at the frequency point f 2. In the absence of metallic foreign bodies, the constant current source sends a current excitation at frequency f1 and the measuring circuit detects the input impedance L of the resonant network 302_1f1And the frequency f1 and the input impedance L_1f1To the memory of the controller 304. In no at allIn the case of a metallic foreign object, the constant current source sends a current excitation at frequency f2 and the measurement circuit detects the input impedance L of the resonant network 302_1f2And the frequencies f2 and L_1f2To the memory of the controller 304. For example, in the absence of metallic foreign objects, the constant current source sends a current excitation at a frequency of 285kHz at f1, and the measurement circuit detects the input impedance L of the resonant network 302_1f1And the frequency f1 is 285kHz and the input impedance L_1f1To the memory of the controller 304. In the absence of metallic foreign bodies, the constant current source sends a current excitation at a frequency f 2-320 kHz, and the measuring circuit detects the input impedance L of the resonant network 302_1f2And the frequency f2 is set to 320kHz and L_1f2To the memory of the controller 304.

S504: determining the input impedance L of the resonant network 302 at frequency point f1 when performing metallic foreign object detection_2f1And an input impedance L at the frequency point f2_2f2. In the detection of the metal foreign matter, the constant current source sends current excitation with the frequency f1, and the measuring circuit 303 detects the input impedance L of the resonant network 302_2f1And the frequency f1 and the input impedance L_2f1To the memory of the controller 304. In the detection of the metal foreign matter, the constant current source sends current excitation with the frequency f2, and the measuring circuit 303 detects the input impedance L of the resonant network 302_2f2And the frequencies f2 and L_2f2To the memory of the controller 304. For example, in the case of metal foreign object detection, the constant current source sends a current excitation at a frequency f 1-285 kHz, and the measurement circuit 303 detects the input impedance L of the resonant network 302_2f1And the frequency f1 is 285kHz and the input impedance L_2f1To the memory of the controller 304. In the detection of the foreign metal, the constant current source sends current excitation with the frequency f 2-320 kHz, and the measuring circuit 303 detects the input impedance L of the resonant network 302_2f2And the frequency f2 is set to 320kHz and L_2f2To the memory of the controller 304.

S505: calculating the preset impedance L of the resonant network 302 at the frequency point f1_1f1And an input impedance L_2f1Δ L1, Δ L1 is the differential impedance at frequency point f 1. In the controller 304, the power of the constant current source is compared when no metal foreign matter existsInput impedance L of resonant network at flow excitation frequency f1_1f1And the input impedance L of the resonant network when the metal foreign matter is detected and the current excitation frequency of the constant current source is f1_2f1Δ L1, Δ L1 ═ L_1f1-L_2f1. When there is no metal foreign matter at the time of metal foreign matter detection, it is understood that L is theoretically_1f1＝L_2f1，ΔL1＝L_1f1-L_2f10. However, since the system parameters may not be exactly the same, L is actually judged_1f1And L_2f1Is less than a threshold, i.e., Δ L1 ═ L_1f1-L_2f1＜L_set1It is considered that no foreign matter is present in the metal foreign matter detection. For example, when f1 is 285kHz, Δ L1 is L when detecting a metal foreign substance_1f1-L_2f1When the foreign metal is detected, no foreign metal is present, L_1f1And L_2f1Is less than a threshold, Δ L1 ═ L_1f1-L_2f1＜L_set1(ii) a When the metallic foreign matter is detected, a metallic foreign matter L is present_1f1And L_2f1Is greater than a threshold, Δ L1 ═ L_1f1-L_2f1＞L_set1. Optionally, Δ L1 may also be calculated for the input impedance L of the resonant network 302 at frequency point f1_2f1And a predetermined impedance L_1f1I.e., Δ L1 ═ L_2f1-L_1f1。

S506: calculating the preset impedance L of the resonant network 302 at the frequency point f2_1f2And an input impedance L_2f2Δ L2, Δ L2 is the differential impedance at frequency point f 2. In the controller 304, the input impedance L of the resonant network is compared when the current excitation frequency of the constant current source is f2 when there is no metallic foreign matter_1f2And the input impedance L of the resonant network when the metal foreign matter is detected and the current excitation frequency of the constant current source is f2_2f2Δ L2, Δ L2 ═ L_1f2-L_2f2. When there is no metal foreign matter at the time of metal foreign matter detection, it is understood that L is theoretically_1f2＝L_2f2，ΔL2＝L_1f2-L_2f20. However, since the system parameters may not be exactly the same, L is actually judged_1f2And L_2f2Is less than a threshold, i.e., Δ L2 ═L_1f2-K_2f2＜L_set2It is considered that no foreign matter is present in the metal foreign matter detection. For example, when f1 is 285kHz, Δ L2 is L when detecting a metal foreign substance_1f2-L_2f2When the foreign metal is detected, no foreign metal is present, L_1f2And L_2f2Is less than a threshold, Δ L2 ═ L_1f2-L_2f2＜L_set2(ii) a When the metallic foreign matter is detected, a metallic foreign matter L is present_1f2And L_2f2Is greater than a threshold, Δ L2 ═ L_1f2-L_2f2＞L_set2. Optionally, Δ L2 may also be calculated for the input impedance L of the resonant network 302 at frequency point f2_2f2And a predetermined impedance L_1f2I.e., Δ L1 ═ L_2f2-L_1f2。

S507: the absolute value Δ L of the impedance difference of the difference impedance at the frequency point f1 and the difference impedance at the frequency point f2 is calculated, Δ L being the total difference impedance. In the controller 304, calculating the absolute value of the impedance difference between the difference impedance at the frequency point f1 and the difference impedance at the frequency point f2 yields the total difference impedance, i.e., Δ L ═ Δ L1- Δ L2 |.

S508: comparing the delta L with a preset threshold value, and judging whether the metal foreign matters exist or not according to the comparison result. Theoretically, when there is no metallic foreign object, Δ L ═ Δ L1- Δ L2| ═ 0, and when there is a metallic foreign object, the presence of the foreign object distorts the induced magnetic field, for example, the metallic foreign object is also induced with an induced electromotive force in a time-varying magnetic field, which electromotive force generates a closed-loop current, i.e., eddy current, inside the metallic foreign object, and the eddy current may generate a magnetic field. Nonmetal foreign matters such as organism foreign matters can also cause the time-varying magnetic field to generate distortion, so the embodiment of the application can also be used for detecting other nonmetal foreign matters. In one possible implementation, the eddy current magnetic field generated by the metallic foreign object may generate an induced electromotive force on the resonant network 302, which in turn may affect the input impedance, i.e., superimpose the foreign object induced impedance on the input impedance of the resonant network 302. As shown in fig. 1, it can be seen from fig. 1 that the impedance of the resonance circuit is large in both cases of the presence and absence of a metallic foreign object on both sides at the frequency ω 1 near the resonance frequency ω rThe smaller is different. When the frequency is less than omega 1, the impedance of the detection circuit when the metal foreign matter exists is greater than the impedance of the resonance circuit when the metal foreign matter does not exist; when the frequency is higher than omega 1, the impedance of the resonance circuit when the metal foreign matter exists is smaller than the impedance of the detection circuit when the metal foreign matter does not exist. However, the direction and magnitude of the difference between the foreign object induced voltage and the input voltage of the resonant network 302 at different frequencies are different, which also results in different input impedances of the resonant network at different frequencies, i.e. Δ L1 is not equal to Δ L2, and Δ L ═ Δ L1- Δ L2| ≠ 0. It is understood that in practical applications, due to the existence of an error, Δ L may not be 0 when no metallic foreign matter exists. Therefore, in order to increase the detection accuracy, a threshold value L can be preset according to the requirements of specific working conditions and error ranges_set. The total differential impedance Δ L is compared with a predetermined threshold value in the controller 304, and when Δ L is greater than the predetermined threshold value range, i.e., Δ L | Δ L1- Δ L2| > L_setThe presence of foreign matter is considered; when Δ L is smaller than a predetermined threshold range, i.e., Δ L ═ Δ L1- Δ L2| < L_setThen, it is considered that no metal foreign matter is present. It can be understood that, in the embodiment of the present application, the method for measuring the impedance difference at two frequencies can effectively improve the detection accuracy and avoid the false detection compared with the method for measuring the impedance difference at one frequency.

It can be seen from fig. 1 that, under the two different situations of no metal foreign matter and metal foreign matter, because the difference values of the impedance characteristic curves of the resonant network at the two sides of the resonant frequency are different, but the induced voltages generated by the common interference signals can be considered to be approximately equal at different frequencies, and the changes to the impedance caused by the induced voltages are also the same, the common interference signals appearing under different complex conditions, such as the interference of the magnetic field change of the transmitting coil and the different coupling coefficients caused by the different relative positions between the transmitting coil and the receiving coil, can be effectively eliminated according to the above method, so that the detection accuracy of the metal foreign matter is improved, the misjudgment is reduced, and the purpose of high-precision metal foreign matter detection is achieved.

For example, there are disturbances caused by the change of the magnetic field of the transmitting coil when the metal foreign matter is detected, and the constant current source when there is no metal foreign matterHas an input impedance L of the resonant network at a current excitation frequency f1_1f1The magnetic field variation of the transmitting coil generates an interference impedance Li at a current excitation frequency f1 of the constant current source₁Then, when detecting a metal foreign object, the constant current source sends a current excitation with frequency f1, and 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 is L when there is no metallic foreign matter and the current excitation frequency of the constant current source is f2_1f2The magnetic field variation of the transmitting coil generates an interference impedance Li at a current excitation frequency f2 of the constant current source₂Then, when detecting a metal foreign object, the constant current source sends a current excitation with frequency f2, and the input impedance of the resonant network 302 detected by the measuring circuit 303 should be L_2f2+Li₂. In the controller 304, the input impedance L of the resonant network is compared when the current excitation frequency of the constant current source is f1 when there is no metallic foreign matter_1f1And in the presence of interference caused by changes in the magnetic field of the transmitting coil, the input impedance L of the resonant network at the time of metal foreign object detection at a current excitation frequency f1 of the constant current source_2f1+Li₁Δ L1, Δ L1 ═ L_1f1-(L_2f1+Li₁). Comparing the input impedance L of the resonant network when the current excitation frequency of the constant current source is f2 without the metallic foreign matter_1f2And in the presence of interference caused by changes in the magnetic field of the transmitting coil, the input impedance L of the resonant network at the time of metal foreign object detection at a current excitation frequency f2 of the constant current source_2f2+Li₂Δ L2, Δ L2 ═ L_1f2-(L_2f2+Li₂). In the controller 304, the total differential impedance Δ L | Δ L1- Δ L2| at the frequency points f1 and f2 is calculated. The induced voltages caused by the magnetic field variation of the transmitting coil can be considered to be approximately equal at different frequencies, and the variation caused to the impedance corresponding to the induced voltages is also the same, i.e. Li₁＝Li₂. Therefore, when there is no metal foreign object, theoretically, the total differential impedance Δ L is | Δ L1- Δ L2| 0, and it can be understood that, in practice, the total differential impedance Δ L is smaller than a threshold value, and there is no misjudgment. Total differential impedance in the presence of foreign matter and no induced impedanceThe total differential impedance is the same when the noise exists and the foreign matter exists, the threshold value setting can also be the same, and the misjudgment can not be generated.

The method embodiments of the second or third embodiment can be applied to the foreign object detection apparatus described in the first embodiment.

It is understood that the difference in the differential voltage or the differential resistance described in the above embodiments may be an actual difference including the direction of the voltage or the resistance, or may be a processed difference, such as an absolute value of the actual difference. The specific situation can be designed according to actual needs, and the application is not limited.

Fourth of the embodiments of this application provides a but wireless transmitting system that charges of foreign matter detection, but this but wireless transmitting system that charges of foreign matter detection includes embodiment one foreign matter detection device and the wireless transmitting device that charges that fig. 4 shows, foreign matter detection device is used for detecting whether have the foreign matter in the wireless transmitting system that charges, no longer describe here.

The fifth embodiment of the present application provides a wireless charging receiving system capable of detecting a foreign object, where the wireless charging receiving system capable of detecting a foreign object includes the first embodiment of the foreign object detecting device and the wireless charging receiving device shown in fig. 4, and the foreign object detecting device is configured to detect whether a foreign object is present in the wireless charging receiving system, which is not described herein again.

Sixth of the embodiment of the application, a wireless charging system capable of detecting foreign matters is provided, and the wireless charging system capable of detecting foreign matters comprises a first foreign matter detection device, a wireless charging transmitting device and a wireless charging receiving device, wherein the wireless charging transmitting device and the wireless charging receiving device are shown in fig. 4, and the foreign matter detection device is used for detecting whether foreign matters exist in the wireless charging system or not, and is not repeated herein.

In the above embodiments, the implementation may be wholly or partially realized by software, hardware, firmware, or any combination thereof. When implemented using a software program, may be implemented in whole or in part in the form of a computer program product. The computer program product includes at least one computer instruction. When loaded and executed on a computer, cause the processes or functions described in accordance with the embodiments of the application to occur, in whole or in part. The computer may be a general purpose computer, a special purpose computer, a network of computers, or other programmable device. The computer instructions may be stored in a computer readable storage medium or transmitted from one computer readable storage medium to another, for example, from one website site, computer, server, or data center to another website site, 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.). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device including at least one available medium integrated server, data center, or the like. The usable medium may 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)), among others.

It should be noted that, for specific descriptions of each step in the method provided in the second or third embodiment of the present application, reference may be made to the specific descriptions of corresponding contents in the apparatus embodiment of the first embodiment, and details are not repeated here. In addition, the method provided by the second or third embodiment of the present application is used to realize the foreign object detection function of the foreign object detection apparatus in the first embodiment, so that the same effects as those of the first embodiment can be achieved.

By using the foreign matter detection method, device or system provided by the embodiment of the application, the influence on the foreign matter detection process caused by the change of the induction voltage of the resonant network caused by the change of the magnetic field of the transmitting coil, such as the change of the output power, the output voltage and the output current of the transmitting coil, can be eliminated, so that the foreign matter detection precision is improved, and the misjudgment is reduced.

Through the above description of the embodiments, it is clear to those skilled in the art that, for convenience and simplicity of description, the foregoing division of the functional modules is merely used as an example, and in practical applications, the above function distribution may be completed by different functional modules according to needs, that is, the internal structure of the device may be divided into different functional modules to complete all or part of the above described functions.

In the several embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the above-described device embodiments are merely illustrative, and for example, the division of the modules or units is only one logical functional division, and there may be other divisions when actually implemented, for example, a plurality of units or components may be combined or may be integrated into another device, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may be one physical unit or a plurality of physical units, that is, may be located in one place, or may be distributed in a plurality of different places. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiments of the present application.

In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.

The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a readable storage medium. Based on such understanding, the technical solutions of the embodiments of the present application may be essentially or partially contributed to by the prior art, or all or part of the technical solutions may be embodied in the form of a software product, where the software product is stored in a storage medium and includes several instructions to enable a device (which may be a single chip, a chip, or the like) or a processor (processor) to execute all or part of the steps of the methods described in the embodiments of the present application. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.

The foregoing is merely a preferred embodiment of the present application and is not intended to limit the present application in any way. Although the present application has been described with reference to the preferred embodiments, it is not intended to limit the present application. Those skilled in the art can now make numerous possible variations and modifications to the disclosed embodiments, or modify equivalent embodiments, using the methods and techniques disclosed above, without departing from the scope of the claimed embodiments. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application still fall within the protection scope of the technical solution of the present application without departing from the content of the technical solution of the present application.

Claims

1. A wireless charging foreign object detection method, the method comprising:

2. The method according to claim 1, wherein the determining whether the foreign object exists according to the third difference voltage specifically comprises:

3. The method of claim 1 or 2, wherein prior to determining the first frequency and the second frequency, the method further comprises:

4. The method of claim 1, wherein the first frequency is selected in a frequency interval [ (f- Δ f), f ], the second frequency is selected in a frequency interval [ f, (f + Δ f) ], wherein f is an actual resonant frequency of the resonant network, and wherein Δ f has a value in an interval [0.01f, 0.5f ].

5. The method according to any of claims 1-4, wherein the resonant network comprises N detection coils, N being an integer greater than or equal to 1.

6. The method according to claim 5, wherein any of the N detection coils comprises a switch, an inductive element, and a capacitive element, the switch being in series with the inductive element, the capacitive element being in parallel with the inductive element.

7. A wireless charging foreign object detection method, the method comprising:

8. The method according to claim 7, wherein the determining whether the foreign object exists according to the third difference impedance specifically comprises:

9. The method according to claim 7 or 8,

prior to determining the first frequency and the second frequency, the method further comprises:

10. The method of claim 7, wherein the first frequency is selected in a frequency interval [ (f- Δ f), f ], the second frequency is selected in a frequency interval [ f, (f + Δ f) ], wherein f is the actual resonant frequency of the resonant network, and wherein Δ f has a value in an interval [0.01f, 0.5f ].

11. The method according to any of claims 7-10, wherein the resonant network comprises N detection coils, N being an integer greater than or equal to 1.

12. The method according to claim 11, wherein any of the N detection coils comprises a switch, an inductive element, and a capacitive element, the switch being in series with the inductive element, the capacitive element being in parallel with the inductive element.

13. A wireless charging foreign object detection device, the device comprising an ac source, a resonant network, a measurement circuit and a controller, wherein:

the controller is used for acquiring 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;

14. The detection apparatus of claim 13, wherein the ac source comprises a constant ac source.

15. The detection device according to claim 13 or 14, wherein the resonant network comprises N detection coils, N being an integer greater than or equal to 1.

16. The detecting device according to claim 15, wherein each of the N detecting coils includes a switch, an inductive element, and a capacitive element, the switch being connected in series with the inductive element, and the capacitive element being connected in parallel with the inductive element.

17. The sensing device of any one of claims 13-16, wherein the measurement circuit is further configured to:

an input impedance of the resonant network is measured.

18. The sensing device of any one of claims 13-17, wherein the controller is further configured to:

19. A wireless charging transmission system, comprising the wireless charging foreign object detection device of claims 13-18 and a wireless charging transmission device, wherein the wireless charging foreign object detection device is configured to detect whether a foreign object is present in the wireless charging transmission system.

20. A wireless charging receiving system, comprising the wireless charging foreign object detection device of claims 13-18 and a wireless charging receiving device, wherein the wireless charging foreign object detection device is configured to detect whether a foreign object is present in the wireless charging receiving system.

21. A wireless charging system, comprising the wireless charging foreign object detection apparatus of claims 13-18 and a wireless charging apparatus, wherein the wireless charging foreign object detection apparatus is configured to detect whether a foreign object is present in the wireless charging system.