CN117118097B - Metal foreign matter detection circuit, method and related device - Google Patents

Abstract

The present application provides a metal foreign body detection circuit, method and related device, the metal foreign body detection circuit includes a first coil and a second coil, the second coil is located outside the first coil. The first end of the second coil is connected to the control circuit corresponding to the coil through a first switch circuit, and the second end is directly connected to the control circuit. The first switch circuit is connected in parallel with the second switch circuit, and the second switch circuit includes a first capacitor and a switch connected in series. By controlling the switching state of the first and second switch circuits, the second coil is connected in series with the first capacitor to obtain an LC resonant circuit, and the quality factor of the LC resonant circuit is obtained. Finally, the metal foreign body located within the position range of the second coil is detected according to the quality factor. It can be seen from the above content that the detection circuit uses the second coil to assist in detecting metal foreign bodies outside the first coil, avoiding the risk of excessive temperature of the metal foreign body due to normal charging without detecting the metal foreign body at the edge of the first coil, thereby improving the safety of the wireless charging process.

Description

Metal foreign body detection circuit, method and related device

Technical Field

The present application relates to the field of wireless charging technology, and in particular to a metal foreign body detection circuit, method and related device.

Background technique

Wireless charging technology mainly uses the principle of electromagnetic induction to achieve power transfer through energy coupling through coils. Coils are set on wireless chargers and electronic devices (i.e., mobile phones, Bluetooth headsets, etc.). A transmitting coil is set in the wireless charger, and a receiving coil is set inside the electronic device. When the electronic device is placed on the wireless charger and the wireless charger is powered on, the AC current on the transmitting coil generates a changing magnetic field. The receiving coil will sense the change in the magnetic field to generate an induced current, and then convert the induced current into DC power to charge the mobile phone battery.

During the wireless charging process, if there are conductive objects such as metal (such as coins, keys) between the wireless charger and the electronic device, eddy currents will be generated inside the magnetic field. The Joule effect of the eddy currents will cause the metal objects to heat up. If the heat cannot be released and accumulates too much, it will cause damage to the wireless charger and electronic device. In severe cases, the battery of the electronic device may overheat and explode.

Summary of the invention

In view of this, the present application provides a metal foreign body detection method and related devices to accurately detect metal foreign bodies, and the disclosed technical solutions are as follows:

In the first aspect, the present application provides a metal foreign body detection circuit, which is applied to an electronic device, the electronic device includes a first coil and a second coil, the first coil is a wireless charging coil, the second coil is located outside the first coil, and the metal foreign body detection circuit includes: the first end of the second coil is connected to the first end of the second coil control circuit through the first switch circuit, and the second end of the second coil is connected to the second end of the second coil control circuit; the second switch circuit is connected in parallel with the first switch circuit, and the second switch circuit includes a first capacitor and a switch connected in series; the second coil control circuit obtains the voltage peak data of the LC resonant circuit in the discharge stage, and calculates the Q value of the LC resonant circuit according to the voltage peak data, the LC resonant circuit includes a second coil and a first capacitor connected in series, and the Q value is used to detect metal foreign bodies within the position range of the second coil. It can be seen from the above content that the detection circuit uses the second coil to assist in detecting metal foreign bodies outside the first coil, avoiding the risk of excessive temperature of the metal foreign body due to normal charging without detecting the metal foreign body at the edge of the first coil, thereby improving the safety of the wireless charging process.

In a possible implementation of the first aspect, the second coil is a near field communication NFC coil. In this way, the accuracy of metal foreign body detection can be improved without increasing hardware costs.

In a possible implementation of the first aspect, the second switching circuit includes a first capacitor and a first switch; the first end of the first capacitor is connected to the first end of the second coil, the second end of the first capacitor is connected to the first end of the first switch, and the second end of the first switch is connected to the first end of the second coil control circuit; or, the first end of the first switch is connected to the first end of the second coil, the second end of the first switch is connected to the first end of the first capacitor, and the second end of the first capacitor is connected to the first end of the second coil control circuit.

In a possible implementation of the first aspect, the second switch circuit includes a first capacitor, a second switch, and a third switch; the first end of the second switch is connected to the first end of the second coil, the second end of the second switch is connected to the first end of the first capacitor, the second end of the first capacitor is connected to the first end of the third switch, and the second end of the third switch is connected to the first end of the second coil control circuit. In this way, switches are connected in series at both ends of the first capacitor, and when the electronic device uses the NFC coil to implement the NFC communication function, the second switch and the third switch are both disconnected, thereby preventing the electrical signal of the first capacitor from being transmitted to the NFC coil, and avoiding the NFC coil from being interfered by C2.

In a possible implementation of the first aspect, the second coil control circuit controls the LC resonant circuit to charge and discharge, and triggers the peak detector to collect voltage peak data of the LC resonant circuit in the discharge stage. This solution is applied to the scenario where the second coil control circuit is provided with a corresponding peak detector, so that when the second coil control circuit controls the charging and discharging of the LC resonant circuit, the peak detector can be directly triggered to collect voltage peak data, thereby realizing rapid collection of required data and further improving the efficiency of metal foreign body detection.

In a possible implementation of the first aspect, the metal foreign object detection circuit includes a first coil control circuit connected to the first coil, the first coil control circuit controls the LC resonant circuit to charge and discharge, and triggers the peak detector to collect voltage peak data of the LC resonant circuit in the discharge stage.

In a possible implementation manner of the first aspect, the first coil control circuit is a wireless charging coil chip, and the second coil control circuit is an NFC chip.

In a possible implementation manner of the first aspect, the metal foreign object detection circuit includes a first coil control circuit connected to the first coil, and the first coil control circuit triggers the second coil control circuit to start.

In a possible implementation of the first aspect, the metal foreign body detection circuit includes a first coil control circuit connected to the first coil, the first coil control circuit controls the first switch circuit to open and the second switch circuit to close, so that the second coil and the first capacitor are connected in series to form an LC resonant circuit; or, the second coil control circuit controls the first switch circuit to open and the second switch circuit to close, so that the second coil and the first capacitor are connected in series to form an LC resonant circuit.

In the second aspect, the present application also provides a metal foreign body detection circuit, which is applied to an electronic device, the electronic device includes a first coil and a second coil, the first coil is a wireless charging coil, and the second coil is located outside the first coil, and the metal foreign body detection circuit includes: the first coil is connected to the first coil control circuit, and the first coil control circuit is used to control the working state of the first coil; the first end of the second coil is connected to the first end of the second coil control circuit through the third switch circuit, and the second end of the second coil is connected to the second end of the second coil control circuit through the fourth switch circuit, and the second coil control circuit is used to control the working state of the second coil; the first end of the second coil is also connected to the first end of the first coil control circuit through the fifth switch circuit, and the second end of the second coil is also connected to the second end of the first coil control circuit through the sixth switch circuit, and the fifth switch circuit includes a first capacitor and a switch connected in series; the first coil control circuit obtains the voltage peak data of the LC resonant circuit in the discharge stage, and the Q value calculated according to the voltage peak data; the first coil control circuit detects the metal foreign body within the range of the second coil according to the Q value. This solution can accurately detect the metal foreign body outside the range of the WPC coil, avoid the risk of excessive temperature of the metal foreign body caused by normal charging without detecting the metal foreign body at the edge of the WPC coil, and ultimately improve the safety of the wireless charging process. Moreover, the solution calculates the Q value of the LC resonant circuit by the RX chip and detects metal foreign objects based on the Q value. Therefore, there is no need to modify the software (i.e., processing logic) and hardware of the NFC chip, saving the cost of modifying the NFC chip and ultimately reducing the cost of the entire metal foreign object detection solution.

In a possible implementation of the second aspect, the second coil is a near field communication NFC coil. In this way, the accuracy of metal foreign body detection can be improved without increasing hardware costs.

In a possible implementation of the second aspect, the first coil control circuit controls the charging and discharging of an LC resonant circuit obtained by connecting the second coil in series with the first capacitor, and triggers a peak detector to detect voltage peak data of the LC resonant circuit during the discharge phase of the LC resonant circuit.

In a possible implementation of the second aspect, the first coil control circuit controls the third switch circuit and the fourth switch circuit to be disconnected, and controls the fifth switch circuit and the sixth switch circuit to be closed, so that the second coil is connected in series with the first capacitor to obtain an LC resonant circuit.

In a possible implementation manner of the second aspect, the first coil control circuit is a wireless charging coil chip, and the second coil control circuit is an NFC chip.

In a third aspect, the present application also provides a metal foreign body detection method, which is applied to an electronic device, and the electronic device includes the metal foreign body detection circuit of any one of the first aspects, and the method includes: controlling the switching state of the switching circuit connected to the second coil, so that the second coil and the first capacitor are connected in series to obtain an LC resonant circuit; controlling the LC resonant circuit to charge and discharge after charging is completed; obtaining voltage peak data of the LC resonant circuit in the discharge stage; calculating the quality factor Q value of the LC resonant circuit based on the voltage peak data, and detecting metal foreign bodies within the position range of the second coil based on the Q value.

In a fourth aspect, the present application also provides a wireless charging system, including a wireless charging base and an electronic device; the wireless charging base includes a first WPC coil and a first NFC coil, the first NFC coil is located outside the first WPC coil; the electronic device includes a second WPC coil and a second NFC coil, the second NFC coil is located outside the second WPC coil; the wireless charging base controls the first NFC coil to transmit a first NFC signal, and when the voltage value of the first NFC signal is detected to be lower than the normal voltage value, it is determined that there is a metal foreign body between the wireless charging base and the electronic device; or, the electronic device controls the second NFC coil to transmit a second NFC signal, and when the voltage value of the second NFC signal is detected to be lower than the normal voltage value, it is determined that there is a metal foreign body between the electronic device and the wireless charging base. It can be seen that the NFC coil can also be set outside the WPC coil in the wireless charging base in the system, and the metal foreign body at the edge of the WPC coil is detected by the NFC coil, thereby improving the metal foreign body detection accuracy of the wireless charging base. Moreover, the system can detect metal foreign bodies by using the voltage change of the NFC signal between the wireless charging base and the electronic device, without the need to connect the NFC coil and the capacitor in series to form an LC resonant circuit, thereby reducing the hardware cost, while improving the metal foreign body detection accuracy, and further improving the safety of the wireless charging process.

In a fifth aspect, the present application also provides a wireless charging base, comprising the metal foreign body detection circuit of any one of the first aspects.

In a sixth aspect, the present application also provides an electronic device, comprising the metal foreign body detection circuit of any one of the first aspects.

In the seventh aspect, the present application also provides a chip system, including: at least one processor and an interface, the interface is used to receive code instructions and transmit them to at least one processor; at least one processor runs the code instructions to implement the metal foreign body detection method of the third aspect.

In an eighth aspect, the present application further provides a computer-readable storage medium having instructions stored thereon, which, when the instructions are executed on an electronic device, enables the electronic device to execute the metal foreign body detection method as in the third aspect.

It should be understood that the description of technical features, technical solutions, beneficial effects or similar language in this application does not imply that all features and advantages can be realized in any single embodiment. On the contrary, it is understood that the description of features or beneficial effects means that specific technical features, technical solutions or beneficial effects are included in at least one embodiment. Therefore, the description of technical features, technical solutions or beneficial effects in this specification does not necessarily refer to the same embodiment. Furthermore, the technical features, technical solutions and beneficial effects described in the present embodiment can also be combined in any appropriate manner. Those skilled in the art will understand that the embodiment can be realized without one or more specific technical features, technical solutions or beneficial effects of a specific embodiment. In other embodiments, additional technical features and beneficial effects can also be identified in a specific embodiment that does not embody all embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is a schematic diagram of a wireless charging system;

FIG2 is a schematic diagram of coil positions in the wireless charging system shown in FIG1 ;

FIG3 is a schematic diagram of a coil structure in a wireless charging base and an electronic device;

FIG4 is a schematic diagram of a coil structure in an electronic device provided in an embodiment of the present application;

FIG5 is a schematic diagram of a coil structure of a wireless charging base provided in an embodiment of the present application;

FIG6 is a schematic diagram of a metal foreign body detection circuit of an electronic device provided in an embodiment of the present application;

FIG7 is a circuit diagram of the metal foreign body detection circuit shown in FIG6 when it is working;

FIG8 is a flow chart of a metal foreign body detection method corresponding to the circuit shown in FIG6 ;

FIG9 is a schematic diagram of another metal foreign body detection circuit of an electronic device provided in an embodiment of the present application;

10 is a flow chart of a metal foreign body detection method corresponding to the circuit shown in FIG. 9 ;

FIG11 is a schematic diagram of another metal foreign body detection circuit of an electronic device provided in an embodiment of the present application;

FIG12 is a schematic diagram of a circuit when the circuit shown in FIG11 is working;

FIG. 13 is a flow chart of a metal foreign body detection method corresponding to the circuit shown in FIG. 11 .

Detailed ways

The terms "first", "second", "third", etc. in the specification, claims and drawings of this application are used to distinguish different objects rather than to limit a specific order.

In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

As shown in FIG. 1 and FIG. 2 , taking the electronic device as a mobile phone as an example, the wireless charging system includes a wireless charging base 1 and a mobile phone 2 .

A wireless power consortium (WPC) coil 11 is provided inside the wireless charging base 1, and the WPC coil inside the wireless charging base 1 is a transmitting coil. A WPC coil 12 is provided inside the mobile phone 2, and when the mobile phone is in a wireless forward charging state (i.e., the wireless charging base charges the battery in the mobile phone), the WPC coil 12 is a receiving coil.

FIG. 3 shows a schematic diagram of a wireless charging base and a coil in an electronic device.

As shown in (1) of Fig. 3 , the coil structure of the wireless charging base includes a magnetic plate 13 and a WPC coil 11. As shown in (2) of Fig. 3 , the coil structure of the electronic device includes a WPC coil 12 and a magnetic plate 14.

Metal foreign body detection in wireless charging systems is mainly achieved through changes in the quality factor value (Q value) or power loss (P _loss = power emitted by the wireless charging base - power received by the electronic device) of the WPC coil.

For example, a preset threshold corresponding to the Q value is set. If the preset threshold corresponding to the Q value is too small, it is very easy to mistakenly trigger the foreign object alarm and cause charging to terminate. Therefore, in order to avoid mistakenly triggering the foreign object alarm, the preset threshold cannot be too small. However, when the metal object is in the position shown by 15 in (1) and (2) of Figure 3, the Q value of the WPC coil 11 of the wireless charging base and the WPC coil 12 of the electronic device changes very little. By comparing the Q value and its corresponding preset threshold, the metal object cannot be detected. The charging system will think that there is no foreign object and charge normally, which will cause the temperature of the metal object to rise, and further may cause damage to the wireless charging base and the electronic device. In severe cases, it may cause the battery in the electronic device to overheat and explode. The same problem exists when using power loss to detect metal foreign objects.

In order to solve the above technical problems, the present application provides a method for detecting metal foreign matter, which adds a coil (which may be called an auxiliary detection coil) in an electronic device or a wireless charging base, and detects whether there is a metal foreign matter between the wireless charging base and the electronic device by detecting the Q value of the auxiliary detection coil. In this way, the detection accuracy of metal foreign matter is improved, and the temperature rise of the metal foreign matter can be controlled, thereby reducing safety risks. The present application does not limit the type of auxiliary detection coil. For example, the auxiliary detection coil can be other existing coils in the electronic device or the wireless charging base, such as a near field communication (NFC) coil in the electronic device, which can improve the detection accuracy of metal foreign matter without increasing the hardware cost.

In some embodiments, the electronic device can be a mobile phone, tablet computer, desktop, laptop, notebook computer, ultra-mobile personal computer (UMPC), handheld computer, netbook, personal digital assistant (PDA), wearable electronic device, smart watch and other devices with wireless charging function.

In an exemplary embodiment of the present application, the electronic device may include a processor, a charging management module, a power management module, a battery, a wireless communication module, etc. In addition, a WPC coil and an NFC coil are also provided inside the electronic device. The wireless communication module in this embodiment may include a WPC chip and an NFC chip.

It is to be understood that the structure illustrated in this embodiment does not constitute a specific limitation on the electronic device. In other embodiments, the electronic device may include more or fewer components than shown in the figure, or combine some components, or split some components, or arrange the components differently. The components shown in the figure may be implemented in hardware, software, or a combination of software and hardware.

In the embodiment of the present application, the WPC chip of the electronic device is used to communicate with the WPC chip in the wireless charging base, and to detect whether there is a metal foreign object between the electronic device and the wireless charging base. In order to distinguish the WPC chip of the electronic device from the WPC chip of the wireless charging base, the WPC chip of the electronic device is referred to as the RX (Receiver) chip, and the WPC chip of the wireless charging base is referred to as the TX (Transmitter) chip.

Electronic devices can wirelessly charge batteries through WPC chips and wireless charging coils. During the wireless charging process, NFC chips and NFC coils are used to assist in detecting whether there are metal foreign objects between the electronic device and the wireless charging base.

The processor may include one or more processing units, and different processing units may be independent devices or integrated into one or more processors. For example, in an embodiment of the present application, the processor includes an application processor (AP).

In an exemplary embodiment of the present application, the WPC chip and the NFC chip can communicate indirectly through the processor. For example, when the WPC chip sends data or instructions to the NFC chip, the WPC chip first sends the data or instructions to the processor, and then the processor forwards it to the NFC chip. Similarly, when the NFC chip sends data or instructions to the WPC, the NFC chip first sends the data or instructions to the processor, and then the processor forwards it to the WPC chip.

In addition, an operating system runs on the above components. For example, operating system, operating system, Operating system, etc. Applications can be installed and run on the operating system, such as settings, gallery, calendar, call, map, etc. In the embodiment of the present application, the user can click the battery function item in the settings APP to enter the battery function page, and then turn on the wireless charging switch on the battery function page, so that the electronic device can be wirelessly charged.

The coil structure of the electronic device provided in the embodiment of the present application will be described below in conjunction with FIG. 4 and FIG. 5 .

In some examples, in order to meet NFC communication requirements (such as NFC is commonly used in mobile payment, smart access control, bus cards, electronic tickets, smart tags and other fields), the electronic device is also provided with an NFC coil and an NFC chip.

In one example, as shown in FIG. 4 , the NFC coil 16 is disposed on the periphery of the WPC coil 12 to implement the NFC function of the electronic device.

For electronic devices with NFC coils arranged around the WPC coil, the metal foreign body detection method of the present application can assist in detecting metal foreign bodies by detecting the Q value of the NFC coil. For example, the Q value of the NFC coil can be calculated to detect whether there is a metal foreign body within the position range of the NFC coil, thereby improving the detection accuracy of the metal foreign body and avoiding the risk of the metal foreign body temperature being too high due to normal charging without detecting the metal foreign body.

In another example, at least two WPC coils may be provided in the electronic device, and the Q value corresponding to any WPC coil may be detected to detect whether there is a metal foreign object in the range corresponding to the WPC coil. For example, one or more WPC coils may be added to the periphery of the original WPC coil 12. By detecting the Q value corresponding to the added WPC coil, it is determined whether there is a metal foreign object in the periphery of the original WPC coil.

In another exemplary embodiment of the present application, at least two coils may be provided in the wireless charging base, for example, at least two coils may be WPC coils, or one may be a WPC coil and the other may be an NFC coil. In this way, the presence of metal foreign matter may be detected by the coils provided at the periphery.

Taking the WPC coil and NFC coil as an example, as shown in FIG5 , other types of coils can be added to the periphery of the WPC coil 11 of the wireless charging base, such as the NFC coil 17. In this way, the wireless charging base can determine whether there is a metal foreign body at the position shown by 15 by detecting the change in the Q value of the NFC coil 17.

In some embodiments, in a scenario where both the wireless charging base and the electronic device are provided with NFC coils, the wireless charging base can determine whether there is a metal foreign object by detecting changes (such as changes in voltage value) in a communication signal (such as an NFC signal).

For example, the electronic device controls its own NFC coil to transmit an NFC signal, and the wireless charging base can detect the voltage value of the transmitted NFC signal. If the voltage value of the transmitted NFC signal is less than the normal voltage value of the NFC signal, it is determined that the impedance between the two coils has changed and there is a metal foreign object. If the voltage value of the transmitted NFC signal is equal to the normal voltage value, it is determined that the impedance between the two coils has not changed and there is no metal foreign object.

Similarly, electronic devices can also determine whether there is a metal foreign object by detecting changes in the voltage value of the NFC signal emitted by the wireless charging base.

In another example, at least two WPC coils may be provided in the wireless charging base, and the Q value or power loss corresponding to any WPC coil may be detected to detect whether there is a metal foreign object within the range of the WPC coil.

The following uses the auxiliary detection coil being an NFC coil as an example to illustrate the metal foreign body detection circuit for an electronic device provided in an embodiment of the present application.

1. NFC chip calculates Q value or detects metal foreign objects

1. There are two peak detectors in the metal foreign body detection circuit, that is, the RX chip and the NFC chip are each equipped with a peak detector

FIG. 6 is a schematic diagram of a metal foreign body detection circuit in an electronic device provided in an embodiment of the present application.

In an exemplary embodiment, a first end of the NFC coil is connected to a pin of the NFC chip through a first switch circuit, and a second end of the NFC coil is connected to another pin of the NFC chip, and a second switch circuit is connected in parallel with the first switch circuit.

In one example, as shown in FIG6 , the first switch circuit includes a first switch SW1, and the second switch circuit includes a capacitor C2 (i.e., a first capacitor), and a second switch SW2 and a third switch SW3 connected in series. One end of the NFC coil is connected to a pin of the NFC chip through the first switch SW1. The two ends of the capacitor C2 are respectively connected in series with the second switch SW2 and the third switch SW3, and the second switch circuit is connected in parallel with the first switch circuit.

In the example shown in FIG6 , SW2 is connected in series between C2 and the NFC coil. When the NFC coil performs NFC communication, SW2 is disconnected, which prevents the electrical signal of C2 from being transmitted to the NFC coil, thereby preventing the NFC coil from being interfered by C2.

In other embodiments, the second switch circuit may include a capacitor C2 and a switch connected in series with C2. For example, a switch may be connected in series with the end of the capacitor C2 connected to the NFC coil, such as SW2 shown in FIG6. For another example, a switch may be connected in series with the end of the capacitor C2 connected to the NFC chip, such as SW3 shown in FIG6.

In other embodiments of the present application, the first switch circuit and the second switch circuit may further include a greater number of switches, and these switches may be connected in series and/or in parallel, which is not limited in the present application.

In addition, one end of C2 is also connected to the input end of the first peak detector. The first peak detector is used to detect the voltage peak data (such as the voltage peak value and the number of oscillation cycles, etc.) of the LC resonant circuit composed of the NFC coil and C2 in series during the discharge phase and provide it to the NFC chip.

Referring to FIG. 6 again, one end of the WPC coil is connected to one end of the capacitor C1, the other end of C1 is connected to a pin of the RX chip, and the other end of the WPC coil is connected to another pin of the RX chip. One end of C1 is also connected to the input end of the second peak detector, which is used to collect the voltage peak data of the LC resonant circuit composed of the WPC coil and C1 in series during the discharge stage and provide it to the RX chip.

In one example, the first peak detector may be integrated into the NFC chip, or may be a device independent of the NFC chip. Similarly, the second peak detector may be integrated into the RX chip, or may be a device independent of the RX chip.

In one example, SW1 can be a depletion-type NMOS tube, which is in a closed state by default. SW2 and SW3 can be enhancement-type NMOS tubes, which are in an open state by default. Of course, in other embodiments, SW1-SW3 can also be other types of switch devices, and this application does not limit the type of switch devices of SW1-SW3. The switch state of SW1-SW3 can be controlled by an RX chip or an NFC chip, and this application does not limit this.

FIG. 7 is a circuit diagram of the metal foreign body detection circuit shown in FIG. 6 when in operation.

As shown in FIG. 7 , when the NFC coil is used to assist in detecting metal foreign objects, SW1 is disconnected, and SW2 and SW3 are closed. In this state, the NFC coil and capacitor C2 form an LC resonant circuit.

The NFC chip first controls the LC resonant circuit to charge, and then controls the LC resonant circuit to discharge, and at the same time, triggers the first peak detector to collect voltage peak data of the LC resonant circuit in the discharge stage.

The first peak detector determines the peak data of the voltage signal in the LC resonant circuit (such as the voltage peak value and the number of oscillation cycles), i.e., the voltage peak data, by collecting the voltage signal of the LC resonant circuit in the discharge phase, and sends it to the NFC chip. The NFC chip calculates the Q value of the LC resonant circuit in the discharge phase based on the voltage peak data. If the Q value is less than or equal to the preset threshold, it is determined that there is a metal foreign body at the location of the NFC coil. It can be seen that metal foreign bodies outside the location of the WPC coil can be detected by the NFC coil and the NFC chip.

In one example, the NFC chip can send the Q value to the RX chip, and the RX chip determines whether there is a metal foreign object at the location of the NFC coil based on the Q value.

In another example, after the NFC chip calculates the Q value, it can directly determine whether there is a metal foreign object at the location of the NFC coil based on the Q value, and send the detection result to the RX chip, which executes corresponding processing logic based on the detection result.

The metal foreign body detection circuit shown in FIG6 is also applicable to the wireless charging base. The difference is that the RX chip in the metal foreign body detection circuit is replaced by the WPC chip on the wireless charging base side, that is, the TX chip. The other contents are the same and will not be repeated here.

In other embodiments of the present application, when the electronic device determines that there is no metal foreign object within the location range of the NFC coil, it continues to detect whether there is a metal foreign object within the location range of the WPC coil. For example, the RX chip can obtain the Q value of the LC resonant circuit formed by the WPC coil in the discharge stage through the second peak detector, and further detect the metal foreign object within the location range of the WPC coil based on the Q value. It will not be repeated here.

In addition, when the NFC coil is used for NFC communication, SW1 is closed, and SW2 and SW3 are opened, that is, the capacitor C2 is not connected to the line between the NFC coil and the NFC chip.

The metal foreign body detection method is described below in conjunction with the metal foreign body detection method flow chart shown in FIG8 . This embodiment is described using wireless forward charging of a mobile phone as an example. The method is applied to a wireless charging system.

As shown in FIG8 , the metal foreign body detection method applied to the electronic device side may include the following steps:

S100, the phone's RX chip is started.

After the mobile phone is started, in the scenario where the mobile phone needs to be wirelessly charged, the application processor can directly start the RX chip to supply power. For example, in one example, after the mobile phone turns on the wireless charging switch, the application processor will directly start the RX chip.

S101, establishing a communication connection between the wireless charging base and the mobile phone.

The TX chip of the wireless charging base establishes a communication connection with the Rx chip in the mobile phone so that the wireless charging base and the mobile phone can communicate. For example, in one example, the Tx chip sends a Ping command to the Rx chip to request to establish communication. After receiving the Ping command, the Rx chip returns a signal strength packet (SignalStrength) (which may include information such as supported power values) and identity information to the TX chip. The identity information is the identity identification information of the RX chip.

S102, the RX chip sends an NFC chip activation instruction to the processor in the mobile phone.

In this embodiment, after the mobile phone establishes a communication connection with the wireless charging base, the NFC chip is activated. For example, in one example, after the RX chip establishes a communication connection with the TX chip, an instruction to activate the NFC chip is sent to a processor (eg, an application processor).

When the NFC coil is used to assist in detecting metal foreign objects, the RX chip is started and then the NFC chip is triggered to start.

When the mobile phone implements the NFC communication function through the NFC chip and the NFC coil, the mobile phone's application processor directly activates the NFC chip. Moreover, when the application processor directly activates the NFC chip, the application processor will not activate the RX chip. In other words, the application processor directly activates the NFC chip or directly activates the RX chip. The application processor will not directly activate the NFC chip and the RX chip at the same time.

S103: The processor responds to the NFC chip activation instruction to trigger the NFC chip to activate.

After receiving the NFC chip activation instruction, the processor of the mobile phone can send an activation instruction to the NFC chip to activate the NFC chip.

S104, the RX chip controls SW1 to be disconnected, and controls SW2 and SW3 to be closed, so that the NFC coil and the capacitor C2 are connected in series to obtain an LC resonant circuit.

In one example, after the RX chip sends an NFC chip startup instruction to the application processor, SW1 in the circuit shown in FIG. 10 is controlled to be disconnected, and at the same time, SW2 and SW3 are controlled to be closed, so that the NFC coil and the capacitor C2 are connected in series to form an LC resonant circuit.

The present application does not limit the execution order of S102 and S104. S102 may be executed first and then S104, the two steps may be executed simultaneously, or S104 may be executed first and then S102.

In other embodiments, after the NFC chip is started, the switch states of SW1 to SW3 may be controlled by the NFC chip. The present application does not limit the controller of the switch states of SW1 to SW3.

S105, the NFC chip controls the LC resonant circuit to charge, and controls the LC resonant circuit to discharge after charging is completed, and simultaneously triggers the first peak detector to detect voltage peak data of the LC resonant circuit in the discharge phase.

In this embodiment, the NFC chip first controls the LC resonant circuit to charge, and then discharges it after charging is completed. For example, at time t0, a 3.3V voltage is injected into the LC resonant circuit to charge the LC resonant circuit, and then the LC resonant circuit is grounded to discharge it.

While controlling the LC resonant circuit to discharge, the first peak detector is triggered to collect the peak value of the voltage signal of the circuit at a preset time interval (such as period T). For example, the voltage signal collected at time _t1 is recorded as V( _t1 ), and the voltage signal collected at time tn is recorded as V( _tn ).

Further, the peak value (voltage peak value) of the voltage signal is determined according to the collected voltage signal, and finally the number of cycles N is obtained.

S106: The NFC chip receives the voltage peak data sent by the first peak detector.

In an example, the voltage peak value data may include the number N of cycles of the voltage signal within the acquisition cycle, and each acquired voltage peak value V(t _i ), 1≤i≤n.

S107: The NFC chip calculates the Q value of the LC resonant circuit formed by the NFC coil based on the voltage peak data.

In one example, the Q value of the LC resonant circuit can be calculated by the following formula:

In the above formula, N is the number of cycles (the number of oscillation cycles of the LC resonant circuit included in the period from t ₁ to t _n ), V(t ₁ ) is the first voltage peak value in the acquisition cycle, and V(t _n ) is the last voltage peak value in the acquisition cycle.

S108, the NFC chip sends the Q value to the processor.

S109, the processor sends the Q value to the RX chip.

Indirect communication between the NFC chip and the RX chip is achieved through S108 and S109.

S110, power transmission between the wireless charging base and the mobile phone.

The wireless charging base transmits electromagnetic wave energy through the WPC coil, and the mobile phone receives the electromagnetic wave energy through the WPC coil and converts the electromagnetic wave energy into alternating current. The mobile phone further converts the alternating current into direct current to charge the battery in the mobile phone.

S111, the RX chip determines whether the Q value is less than or equal to a preset threshold, and if so, executes S112; if not, executes S113.

After the RX chip detects the transmission power between the mobile phone and the wireless charging base, it determines whether the Q value is less than or equal to the preset threshold.

A higher Q value indicates a lower decay rate of the energy stored in the LC resonant circuit, and a lower Q value indicates a higher decay rate of the energy in the LC resonant circuit.

The preset threshold value may be obtained according to the actual situation of the NFC coil. For example, NFC coils of different specifications may correspond to different preset threshold values.

For example, in one example, the preset threshold of the Q value is 60. If the Q value of the LC resonant circuit is ≤60, it indicates that there is a metal foreign body between the two. The metal foreign body absorbs the electromagnetic wave energy, causing the energy decay of the LC resonant circuit to become faster and the Q value to decrease. Therefore, when it is detected that the Q value is less than or equal to the preset threshold, it is determined that there is a metal foreign body between the wireless charging base and the mobile phone.

S112, the RX chip generates a foreign object alarm signal, and sends an End Power Transfer (EPT) signal to the wireless charging base to notify it to end charging.

After the RX chip of the mobile phone detects a metal foreign object, it generates a foreign object alarm signal. The foreign object alarm signal can be a sound signal, a light signal, or a graphic information displayed on the mobile phone display interface to remind the user that there is a foreign object between the wireless charging base and the mobile phone.

At the same time, the mobile phone sends an EPT signal to the wireless charging base. After receiving the EPT signal, the wireless charging base terminates the power transmission between the mobile phone and the wireless charging base.

S113, the RX chip determines the charging power according to the Q value and selects a matching coil for charging.

For example, if the Q value is in the range of 80 to 100, it means that the coil on the mobile phone side is aligned with the center of the coil on the wireless charging base, and the mobile phone can be charged at full power. If the Q value is in the range of 60 to 80, it means that the coil on the mobile phone side is not aligned with the coil on the wireless charging base, and the mobile phone can be charged at partial power.

In this embodiment, the NFC chip calculates the Q value of the LC resonant circuit according to the voltage peak data of the LC resonant circuit in the discharge phase collected by the first peak detector.

Moreover, when it is determined that there is no metal foreign matter in the location range of the NFC coil (the location range of the NFC coil in this article refers to the area covered by the NFC coil), the mobile phone will further detect whether there is a metal foreign matter in the location range of the WPC coil. That is, the Q value of the LC resonant circuit formed by the WPC coil and the capacitor C1 is detected in the discharge stage, and the presence of a metal foreign matter is further determined based on the Q value. This application will not elaborate on this process.

S114, after the wireless charging base establishes a communication connection with the mobile phone, obtain the Q value corresponding to the coil in the base, and determine whether the Q value is less than a preset threshold; if so, execute S115; if not, execute S113.

After the wireless charging base establishes a communication connection with the mobile phone, while the above-mentioned metal foreign object detection is performed on the mobile phone side, the wireless charging base side will also detect whether there is a metal foreign object. The wireless charging base can use the LC resonant circuit formed by the WPC coil in the base and detect the Q value of the LC resonant circuit. Finally, the metal foreign object is judged based on the Q value. This process is the same as the process of the mobile phone detecting metal foreign objects through the WPC coil in the mobile phone, and will not be repeated here.

The timing of the wireless charging base detecting the Q value of the LC resonant circuit is the same as that of the mobile phone, for example, it can be performed after the mobile phone and the wireless charging base establish a communication connection. In addition, the timing of judging the metal foreign body based on the Q value is also the same as that of the mobile phone, for example, judging the metal foreign body based on the Q value after the wireless charging base and the mobile phone have performed power transmission.

S115, the wireless charging base issues a foreign object alarm and ends charging.

The foreign object alarm method of the wireless charging base is the same as that of the mobile phone side, so I will not go into details here.

It should be noted that whether the mobile phone detects a metal foreign object or the wireless charging base detects a metal foreign object, a foreign object alarm will be generated and charging will be terminated.

The metal foreign body detection method provided in this embodiment, after the WPC chip (RX chip) on the mobile phone side is started, the NFC chip is triggered to start, and the NFC coil and capacitor C2 are controlled to form an LC resonant circuit. The voltage peak data of the LC resonant circuit in the discharge stage is collected by the first peak detector corresponding to the NFC chip, and the NFC chip calculates the Q value according to the voltage peak data and sends it to the RX chip. The RX chip detects whether there is a metal foreign body within the range of the NFC coil according to the Q value. If there is a metal foreign body, the RX chip sends a foreign body alarm signal, and at the same time sends a termination charging instruction to the wireless charging base to terminate the wireless charging process. It can be seen that this scheme expands the detection range of metal foreign bodies, thereby avoiding the risk of excessive temperature of metal foreign bodies caused by normal charging without detecting metal foreign bodies located at the edge of the WPC coil, and ultimately improves the safety of the wireless charging process. Moreover, the embodiment of the present application can use the existing NFC coil of the electronic device to assist in the detection of metal foreign bodies, and improve the detection accuracy of metal foreign bodies without increasing the hardware cost.

In the embodiment shown in FIG8 , the NFC chip calculates the Q value based on the voltage peak data collected by the first peak detector, and the RX chip further detects whether there is a metal foreign body based on the Q value. In other embodiments of the present application, the NFC chip can calculate the Q value based on the voltage peak data, and detect whether there is a metal foreign body based on the Q value, and then send the detection result to the RX chip. The RX chip executes the corresponding processing logic based on the received detection result, which will not be repeated here.

2. A peak detector is set in the metal foreign body detection circuit

FIG9 shows a schematic diagram of another metal foreign body detection circuit of an electronic device provided in an embodiment of the present application. In this embodiment, only one peak detector is provided, and the peak detector is controlled by the RX chip. In addition, the peak detector can be integrated into the RX chip, or be independent of the RX chip and the NFC chip.

As shown in FIG9 , a first input terminal of the peak detector is connected to an LC resonant circuit obtained by connecting an NFC coil and a capacitor C2 in series, and a second input terminal of the peak detector is connected to an LC resonant circuit obtained by connecting a WPC coil and a capacitor C1 in series.

Similar to the metal foreign body detection circuit shown in FIG7 , in the metal foreign body detection circuit shown in FIG10 , SW1 to SW3 can be controlled by the NFC chip or the RX chip. When SW1 is disconnected and SW2 and SW3 are closed, the NFC coil is connected in series with C2 to obtain an LC resonant circuit.

The NFC chip controls the charging and discharging process of the LC resonant circuit obtained by connecting the NFC coil in series with C2. When controlling the LC resonant circuit to start discharging, the processor sends a signal to trigger the peak detector to collect data, so that the peak detector collects the voltage peak data of the LC resonant circuit.

In one example, the peak detector detects the voltage peak data of the LC resonant circuit and provides it to the NFC chip via the RX chip. The NFC chip calculates the Q value based on the voltage peak data and further determines whether there is a metal foreign object based on the Q value.

In another example, the peak detector detects the voltage peak data of the LC resonant circuit and provides it to the RX chip, which calculates the Q value based on the voltage peak data and further determines whether there is a metal foreign object based on the Q value.

FIG. 10 is a flow chart of metal foreign body detection of the metal foreign body detection circuit shown in FIG. 9 . As shown in FIG. 10 , the metal foreign body detection method may include the following steps:

The implementation process of S201 to S204 is the same as the process of S101 to S104 in FIG. 8 , and will not be described in detail here.

S205, the NFC chip controls the charging and discharging process of the LC resonant circuit, and sends a voltage peak acquisition instruction to the processor when the LC resonant circuit starts to discharge.

S206: The processor sends a voltage collection instruction to the RX chip.

S207, the RX chip responds to the voltage peak value collection instruction and triggers the peak value detector to collect the voltage peak value data of the LC resonant circuit.

S205 to S207 of this embodiment realize that when the NFC chip controls the LC resonant circuit to start discharging, the peak detector is triggered to collect the voltage signal.

In the metal foreign body detection circuit shown in FIG9 , the NFC chip controls the charging and discharging process of the LC resonant circuit obtained by connecting the NFC coil in series with C2, and the RX chip triggers the peak detector to collect voltage peak data. Therefore, in this embodiment, when the NFC chip controls the LC resonant circuit to start discharging, the processor sends a voltage signal collection instruction to the RX chip, and the RX chip triggers the peak detector to collect the voltage signal of the LC resonant circuit.

S208, the peak detector sends voltage peak data to the RX chip.

S209, power is transmitted between the wireless charging base and the mobile phone.

S210, the RX chip calculates the Q value corresponding to the LC resonant circuit according to the voltage peak data.

The process of calculating the Q value in S210 of this embodiment is the same as S107 in FIG. 8 , and will not be described in detail here.

S211, the RX chip determines whether the Q value is less than or equal to a preset threshold.

If the Q value is less than or equal to the preset threshold, S212 is executed. If the Q value is greater than the preset threshold, S214 is executed.

S212, the RX chip generates a foreign object alarm signal.

S213, the RX chip sends an EPT packet to the wireless charging base to notify it to end charging.

S214, the RX chip determines the charging power according to the Q value and selects a matching coil for charging.

In addition, when it is determined that there is no metal foreign object within the location range of the NFC coil, the mobile phone will continue to detect whether there is a metal foreign object within the location range of the WPC coil. The detection process is the same as the corresponding process of the embodiment shown in Figure 8, and will not be repeated here.

S215, after the wireless charging base establishes a communication connection with the mobile phone, obtain the Q value corresponding to the coil in the base, and determine whether the Q value is less than a preset threshold; if so, execute S216; if not, execute S214.

S216, the wireless charging base issues a foreign object alarm and ends charging.

The implementation process of S211 to S216 in this embodiment is the same as the process of S111 to S115 in FIG. 8 , and will not be repeated here.

In the metal foreign body detection method provided in this embodiment, the NFC chip controls the charging and discharging process of the LC resonant circuit, and the RX chip collects the voltage peak data of the LC resonant circuit during the discharge phase and calculates the Q value, and further determines whether there is a metal foreign body based on the Q value. In this way, the NFC chip does not need to be configured with a peak detector, further reducing the hardware cost.

2. The WPC chip (RX chip) of the electronic device calculates the Q value and further determines whether there is metal foreign matter based on the Q value

In this embodiment, the RX chip controls the charging and discharging process of the LC resonant circuit formed by the NFC coil and the capacitor C2, calculates the Q value of the LC resonant circuit, and detects whether there is a metal foreign object within the position of the NFC coil.

In order to achieve the above-mentioned purpose of calculating the Q value by the RX chip and judging whether there is a metal foreign body according to the Q value, the embodiment of the present application provides another metal foreign body detection circuit, in which one end of the NFC coil is connected to a pin of the NFC chip through the third switch circuit, and at the same time, the end of the NFC coil is also connected to a pin of the RX chip through the fifth switch circuit. The other end of the NFC coil is connected to another pin of the NFC chip through the fourth switch circuit, and at the same time, the end is also connected to another pin of the RX chip through the sixth switch circuit.

In one example, as shown in FIG11 , one end of the NFC coil is connected to one end of SW11, and the other end of SW11 is connected to a pin of the NFC chip. At the same time, this end of the NFC coil is also connected to one end of SW13, and the other end of SW13 is connected to one end of capacitor C2, and the other end of C2 is connected to a pin of the RX chip (which may be called the first pin). The other end of the NFC coil is connected to another pin of the NFC coil through SW12. At the same time, this end of the NFC coil is also connected to another pin of the RX chip (which may be called the second pin) through SW14.

In the example shown in FIG. 11 , the third switch circuit includes SW11 , the fourth switch circuit includes SW12 , the fifth switch circuit includes SW13 and capacitor C2 connected in series, and the sixth switch circuit includes SW14 .

Of course, in other embodiments, the third, fourth, fifth, and sixth switch circuits may also include two or more switches, and these switches may be connected in series and/or in parallel, which is not limited in the present application.

Referring to FIG. 11 again, one end of the WPC coil is connected in series with the capacitor C1 and then connected to the third pin of the RX chip, and the other end of the WPC coil is connected to the fourth pin of the RX chip.

One input end (referred to as the first input end) of the peak detector is connected to the branch where the capacitor C2 is located, and is used to detect the voltage peak of the LC resonant circuit formed by the NFC coil and C2 during the discharge phase.

The other input end of the peak detector (which may be referred to as the second input end) is connected to the branch where the capacitor C1 is located, and is used to detect the voltage peak of the LC resonance circuit formed by the WPC coil and C1 during the discharge stage.

The peak detector may be integrated into the RX chip, or may be a device independent of the RX chip. The present application does not limit the packaging form of the peak detector.

In one example, SW11 and SW12 may use depletion-type NMOS transistors, which are closed by default. SW13 and SW14 may use enhancement-type NMOS transistors, which are open by default. The switch states of SW11 to SW14 may be controlled by the RX chip. SW11 to SW14 may also use other types of switch devices, and the present application does not limit the types of switch devices.

As shown in FIG. 11 , when SW11 and SW12 are closed, the NFC coil is connected to the NFC chip, and the NFC chip controls the NFC coil to send and receive instructions or data, so that the electronic device can realize the NFC communication function through the NFC coil and the NFC chip.

FIG. 12 is a circuit diagram of the metal foreign body detection circuit shown in FIG. 11 when it is working.

As shown in Figure 12, when SW11 and SW12 are disconnected, and SW13 and SW14 are closed, the NFC coil and capacitor C2 are connected in series to form an LC resonant circuit and connected to the RX chip. The RX chip controls the charging and discharging process of the LC resonant circuit, and triggers the peak detector to collect the voltage peak data of the LC resonant circuit when controlling the discharge of the LC resonant circuit. The RX chip further calculates the Q value of the LC resonant circuit based on the voltage peak data, and finally determines whether there is a metal foreign body based on the Q value.

The process of detecting metal foreign matter is described in detail below in conjunction with the metal foreign matter detection method flow chart shown in FIG. 13 .

As shown in FIG13 , the metal foreign body detection method may include the following steps:

S300, the phone's RX chip is started.

S301, establishing a communication connection between the wireless charging base and the mobile phone.

S302, the RX chip controls SW11 and SW12 to be disconnected, and SW13 and SW14 to be closed, so that the NFC coil and the capacitor C2 are connected in series to obtain an LC resonant circuit.

S303, the RX chip controls the charging and discharging process of the LC resonant circuit, and triggers the peak detector to collect voltage peak data when discharging starts.

S304, the RX chip calculates the Q value based on the voltage peak data.

S307, the RX chip determines whether the Q value is less than or equal to a preset threshold, and if so, executes S308; if not, executes S310.

S308, the RX chip generates a foreign object alarm signal.

S309, the RX chip sends an EPT signal to the wireless charging base to terminate charging.

S310, the RX chip determines the charging power according to the Q value and selects a matching coil for charging.

In addition, when it is determined that there is no metal foreign object within the location range of the NFC coil, the RX chip can continue to determine whether there is a metal foreign object within the location range of the WPC coil. The detection process is the same as the corresponding process of the embodiment shown in Figure 9, and will not be repeated here.

S311, after the wireless charging base establishes a communication connection with the mobile phone, obtain the Q value corresponding to the coil in the base, and determine whether the Q value is less than a preset threshold; if so, execute S312; if not, execute S310.

S312: The wireless charging base issues a foreign object alarm and terminates charging.

The implementation process of S311 to S3120 in this embodiment is the same as S114 to S115 in the embodiment shown in FIG8 , and will not be described again here.

The metal foreign body detection method provided in this embodiment, after the WPC chip (ie, RX chip) on the mobile phone side is started, controls the switch circuit to connect the NFC coil and C2 in series to obtain an LC resonant circuit, and controls the charging and discharging process of the LC resonant circuit, and at the same time triggers the peak detector to collect the voltage peak data of the LC resonant circuit in the discharge stage. The RX chip further calculates the Q value of the LC resonant circuit based on the voltage peak data, and detects whether there is a metal foreign body within the range of the NFC coil according to the Q value. It can be seen that the scheme can accurately detect metal foreign bodies outside the range of the WPC coil, avoid the risk of excessive temperature of the metal foreign body caused by normal charging without detecting the metal foreign body located at the edge of the WPC coil, and ultimately improve the safety of the wireless charging process. Moreover, the scheme calculates the Q value of the LC resonant circuit by the RX chip and detects the metal foreign body according to the Q value. Therefore, there is no need to modify the software (ie, processing logic) and hardware of the NFC chip, saving the cost of modifying the NFC chip, and ultimately reducing the cost of the entire metal foreign body detection scheme.

The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims (18)

1. A metal foreign body detection circuit, characterized in that it is applied to an electronic device, the electronic device comprises a first coil and a second coil, wherein the first coil is a wireless charging coil, and the second coil is a near field communication NFC coil and is located outside the first coil; the metal foreign body detection circuit comprises: The first end of the first coil is connected to the first end of the first coil control circuit through the second capacitor, the second end of the first coil is connected to the second end of the first coil control circuit, and the first coil control circuit is a wireless charging coil chip; The first coil control circuit obtains first voltage peak data of a first LC resonant circuit obtained by connecting the first coil and the second capacitor in series during a discharge phase, and calculates a first Q value of the first LC resonant circuit according to the first voltage peak data, wherein the first Q value is used to detect metal foreign matter within a range where the first coil is located; The first end of the second coil is connected to the first end of the second coil control circuit through the first switch circuit, the second end of the second coil is connected to the second end of the second coil control circuit, and the second coil control circuit is an NFC chip; A second switch circuit is connected in parallel with the first switch circuit, wherein the second switch circuit includes a first capacitor and a switch connected in series; When the first switch circuit is disconnected and the second switch circuit is closed, the second coil control circuit obtains voltage peak data of the second LC resonant circuit in the discharge stage, and calculates a second Q value of the second LC resonant circuit based on the voltage peak data. The second LC resonant circuit includes the second coil and the first capacitor connected in series. The second Q value is used to detect metal foreign objects within the range where the second coil is located. 2. The metal foreign body detection circuit according to claim 1, characterized in that the second switch circuit comprises the first capacitor and a first switch; A first end of the first capacitor is connected to a first end of the second coil, a second end of the first capacitor is connected to a first end of the first switch, and a second end of the first switch is connected to a first end of the second coil control circuit; Alternatively, a first end of the first switch is connected to a first end of the second coil, a second end of the first switch is connected to a first end of the first capacitor, and a second end of the first capacitor is connected to a first end of the second coil control circuit. 3. The metal foreign body detection circuit according to claim 1, characterized in that the second switch circuit comprises the first capacitor, a second switch and a third switch; The first end of the second switch is connected to the first end of the second coil, the second end of the second switch is connected to the first end of the first capacitor, the second end of the first capacitor is connected to the first end of the third switch, and the second end of the third switch is connected to the first end of the second coil control circuit. 4. The metal foreign body detection circuit according to any one of claims 1-3 is characterized in that the second coil control circuit controls the second LC resonant circuit to charge and discharge, and triggers the peak detector to collect voltage peak data of the second LC resonant circuit in the discharge stage. 5. The metal foreign body detection circuit according to any one of claims 1 to 3 is characterized in that the first coil control circuit controls the second LC resonant circuit to charge and discharge, and triggers the peak detector to collect voltage peak data of the second LC resonant circuit in the discharge stage. 6. The metal foreign body detection circuit according to any one of claims 1 to 3, characterized in that the first coil control circuit triggers the second coil control circuit to start. 7. The metal foreign body detection circuit according to any one of claims 1 to 3, characterized in that the first coil control circuit controls the first switch circuit to be disconnected and controls the second switch circuit to be closed; Alternatively, the second coil control circuit controls the first switch circuit to open and controls the second switch circuit to close. 8. A metal foreign body detection circuit, characterized in that it is applied to an electronic device, the electronic device comprises a first coil and a second coil, the first coil is a wireless charging coil, and the second coil is located outside the first coil, the metal foreign body detection circuit comprises: The first coil is connected to a first coil control circuit, and the first coil control circuit is used to control the working state of the first coil; The first end of the second coil is connected to the first end of the second coil control circuit through the third switch circuit, and the second end of the second coil is connected to the second end of the second coil control circuit through the fourth switch circuit, and the second coil control circuit is used to control the working state of the second coil; The first end of the second coil is further connected to the first end of the first coil control circuit through a fifth switch circuit, and the second end of the second coil is further connected to the second end of the first coil control circuit through a sixth switch circuit, wherein the fifth switch circuit includes a first capacitor and a switch in series; The first coil control circuit acquires voltage peak data of the LC resonant circuit in a discharge phase, and a Q value calculated according to the voltage peak data; The first coil control circuit detects metal foreign matter within a range where the second coil is located according to the Q value. 9 . The metal foreign body detection circuit according to claim 8 , wherein the second coil is a near field communication (NFC) coil. 10. The metal foreign body detection circuit according to claim 8 or 9 is characterized in that the first coil control circuit controls the LC resonant circuit obtained by connecting the second coil in series with the first capacitor to charge and discharge, and in the discharge phase of the LC resonant circuit, triggers the peak detector to detect the voltage peak data of the LC resonant circuit. 11. The metal foreign body detection circuit according to claim 8 or 9 is characterized in that the first coil control circuit controls the third switch circuit and the fourth switch circuit to be disconnected, and controls the fifth switch circuit and the sixth switch circuit to be closed, so that the second coil is connected in series with the first capacitor to obtain an LC resonant circuit. 12 . The metal foreign body detection circuit according to claim 8 , wherein the first coil control circuit is a wireless charging coil chip, and the second coil control circuit is an NFC chip. 13. A metal foreign body detection method, characterized in that it is applied to an electronic device, the electronic device comprising the metal foreign body detection circuit according to any one of claims 1 to 12, the method comprising: Controlling the first LC resonant circuit to charge, and to discharge after charging is completed, and obtaining first voltage peak data of the first LC resonant circuit in a discharging stage; Calculating a first Q value of the first LC resonant circuit according to the first voltage peak data, and detecting a metal foreign body within a position range of the first coil according to the first Q value; Controlling the switch state of the switch circuit connected to the second coil so that the second coil is connected in series with the first capacitor to obtain a second LC resonant circuit; Controlling the second LC resonant circuit to charge, and discharge after charging is completed; Acquiring voltage peak data of the second LC resonant circuit in a discharge phase; A second Q value of the second LC resonant circuit is calculated according to the voltage peak data, and a metal foreign object within the position range of the second coil is detected according to the second Q value. 14. A wireless charging system, comprising a wireless charging base and an electronic device, wherein the electronic device comprises the metal foreign body detection circuit according to any one of claims 1 to 12; The wireless charging base comprises a first WPC coil and a first NFC coil, wherein the first NFC coil is located outside the first WPC coil; The electronic device comprises a second WPC coil and a second NFC coil, wherein the second NFC coil is located outside the second WPC coil; The wireless charging base controls the first NFC coil to transmit a first NFC signal, and determines that there is a metal foreign object between the wireless charging base and the electronic device when detecting that a voltage value of the first NFC signal is lower than a normal voltage value; Alternatively, the electronic device controls the second NFC coil to transmit a second NFC signal, and determines that there is a metal foreign object between the electronic device and the wireless charging base when detecting that the voltage value of the second NFC signal is lower than a normal voltage value. 15. A wireless charging base, characterized by comprising the metal foreign body detection circuit according to any one of claims 1 to 12. 16. An electronic device, characterized by comprising the metal foreign body detection circuit according to any one of claims 1 to 12. 17. A chip system, characterized in that it comprises: at least one processor and an interface, wherein the interface is used to receive code instructions and transmit them to the at least one processor; the at least one processor runs the code instructions to implement the metal foreign body detection method described in claim 13. 18. A computer-readable storage medium, characterized in that instructions are stored thereon, and when the instructions are executed on an electronic device, the electronic device executes the metal foreign body detection method according to claim 13.