CN114097180B

CN114097180B - NFC equipment

Info

Publication number: CN114097180B
Application number: CN202080047810.6A
Authority: CN
Inventors: 袁广凯
Original assignee: Shenzhen Goodix Technology Co Ltd
Current assignee: Shenzhen Goodix Technology Co Ltd
Priority date: 2020-12-28
Filing date: 2020-12-28
Publication date: 2023-07-28
Anticipated expiration: 2040-12-28
Also published as: WO2022140957A1; CN114097180A

Abstract

The application provides an NFC equipment, NFC equipment include filter circuit, matching circuit, data reception branch road, NFC controller and NFC antenna, still include: the self-capacitance detection module is used for detecting the capacitance variation of the NFC antenna, wherein the capacitance detection end of the self-capacitance detection module is connected with the positive phase end or the negative phase end of the NFC antenna. The NFC device can achieve detection of the target device through relatively small power consumption.

Description

NFC equipment

Technical Field

The present disclosure relates to the field of NFC communications, and in particular, to an NFC device.

Background

When a near field communication (Near Field Communication, NFC) device is used as an initiator device in NFC communication, detection of a target device, which is also an NFC device, needs to be performed based on an NFC antenna. The current detection method is as follows: an impedance detection module is arranged in an NFC controller (NFCC) of the NFC equipment, polling signals with the duration of tens of microseconds are sent through a TXP port and a TXN port of the NFC controller, impedance change between the TXP port and the TXN port is detected, and if the impedance change reaches a preset threshold value, the existence of target equipment in the environment is judged.

However, this target device detection manner makes the power consumption of the NFC device larger.

Disclosure of Invention

The application provides an NFC device, which can detect target devices through the NFC device through relatively small power consumption.

In a first aspect, an embodiment of the present application provides a near field communication NFC device, where the NFC device includes: the NFC antenna, be used for carrying out signal filtering's filter circuit, be used for carrying out NFC antenna impedance match's matching circuit, be used for transmitting the data signal's that NFC antenna received data receiving branch road, be used for control signal transmission and receiving NFC controller, NFC equipment still includes: the self-capacitance detection module is used for detecting capacitance variation of the NFC antenna, and the capacitance variation is used for judging whether target equipment is close to the NFC antenna or not.

The NFC device detects the target device by detecting the capacitance variation of the NFC antenna through the self-capacitance detection module, and compared with the mode that the impedance detection module detects and transmits a polling signal with the duration of tens of microseconds for each time in the prior art, the self-capacitance detection module has relatively smaller power consumption.

In one possible implementation manner, the capacitance detection end of the self-capacitance detection module is connected to the positive phase end or the negative phase end of the NFC antenna through the matching circuit.

In one possible implementation manner, the capacitance detection end of the self-capacitance detection module is connected to the positive phase end or the negative phase end of the NFC antenna through the data receiving branch.

In one possible implementation manner, the capacitance detection end of the self-capacitance detection module is connected to the positive phase end or the negative phase end of the NFC antenna sequentially through the data receiving branch and the matching circuit.

In one possible implementation, the self-capacitance detection module is located in the NFC controller.

In one possible implementation manner, the capacitance detection end of the self-capacitance detection module is connected to a first end of a first switch, a second end of the first switch is connected to a positive phase end or a negative phase end of the NFC antenna, the first switch is used for being turned on when the self-capacitance detection module works, and the self-capacitance detection module is turned off when the self-capacitance detection module does not work.

In one possible implementation manner, the NFC device includes a matching circuit and a filtering circuit of the NFC antenna, and a ground terminal of a capacitor included in the matching circuit and the filtering circuit is grounded through a fourth switch, where the fourth switch is used to be turned off when the self-capacitance detection module works.

In one possible implementation, the self-capacitance detection module includes:

the capacitor detection end of the self-capacitance detection module is connected with a power supply voltage end through a seventh switch, grounded through an eighth switch, connected with a non-inverting input end of the differential amplifier through a ninth switch, connected with a first end of a ninth capacitor through a tenth switch, and grounded through a second end of the ninth capacitor;

the first end of the ninth capacitor is also connected with a power supply voltage end through an eleventh switch and grounded through a twelfth switch;

the inverting input end of the differential amplifier is connected with a common-mode voltage end, the first output end and the second output end are used for outputting voltage, and the output voltage is related to the capacitance variation of the NFC antenna;

the non-inverting input end of the differential amplifier is also connected with the first output end of the differential amplifier through a third resistor, or a tenth capacitor, or a third resistor and a tenth capacitor which are connected in parallel, and the inverting input end of the differential amplifier is connected with the second output end of the differential amplifier through a fourth resistor, or an eleventh capacitor, or a fourth resistor and an eleventh capacitor which are connected in parallel.

In one possible implementation manner, the capacitance value of the ninth capacitor is equal to a first equivalent capacitance value, where the first equivalent capacitance value is an equivalent capacitance value of an external circuit of the self-capacitance detection module between the capacitance detection end and the power ground end when no target device approaches the NFC antenna, and the voltage of the common-mode voltage end is 1/2 of the power voltage.

In one possible implementation manner, the self-capacitance detection module is specifically configured to: generating a voltage signal based on the capacitance variation of the NFC antenna; the NFC device further includes: the judging module is used for judging whether the amplitude of the first signal output by the self-capacitance detection module exceeds a preset threshold value, if so, judging that the target equipment is close to the NFC antenna, and if not, judging that no target equipment is close to the NFC antenna.

In one possible implementation manner, the NFC controller is configured to determine whether a target device is close to the NFC antenna according to the capacitance variation.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic structural diagram of an example of an NFC device;

FIG. 2 is a schematic diagram of a detection process in a prior art impedance detection method;

fig. 3 is a schematic structural diagram of one embodiment of an NFC device of the present application;

fig. 4 is a schematic structural diagram of one embodiment of an NFC device of the present application;

fig. 5 is a schematic structural diagram of an embodiment of an NFC device of the present application;

fig. 6 is a schematic structural diagram of one embodiment of an NFC device of the present application;

fig. 7 is a schematic structural diagram of an embodiment of an NFC device of the present application;

fig. 8 is an equivalent circuit diagram of the NFC device structure shown in fig. 7 of the present application;

fig. 9 is a schematic structural diagram of one embodiment of an NFC device of the present application;

fig. 10 is an equivalent circuit diagram of the NFC device structure shown in fig. 9 of the present application;

fig. 11 is a schematic structural diagram of an embodiment of an NFC device of the present application;

fig. 12 is a schematic structural diagram of an embodiment of an NFC device of the present application;

fig. 13 is an equivalent circuit diagram of the NFC device structure shown in fig. 12 of the present application;

FIG. 14 is a schematic diagram illustrating the structure of one embodiment of a self-capacitance detection module according to the present application;

FIG. 15 is a timing diagram illustrating the operation of the self-capacitance sensing circuit of FIG. 14 according to the present application;

fig. 16 is a schematic structural diagram of an embodiment of an NFC device of the present application.

Detailed Description

The terminology used in the description section of the present application is for the purpose of describing particular embodiments of the present application only and is not intended to be limiting of the present application.

In general, the NFC device structure is shown in fig. 1, and includes: NFCC, NFC antenna, matching module and filtering module. The filtering module may be used to perform signal filtering, the matching module may be used to perform impedance matching of the NFC antenna, and the NFCC may be used to control signal transmission and reception, where the signal transmitted and received by the NFCC is typically a signal related to the NFC communication protocol. The NFC communication protocol may be an NCI controller interface (NFC Controller Interface, NCI), or the like. The NFCC generally includes a data interaction module, configured to acquire a data signal received by the NFC antenna. The first end and the second end of the data interaction module can be respectively connected with the first receiving end RXP and the second receiving end RXN of the NFCC, and further are respectively connected with two ends of the NFC antenna through the first data transmission branch and the second data transmission branch so as to acquire data signals received by the NFC antenna.

Current target device detection is based on the phenomenon that the impedance of the NFC antenna changes when the target device approaches. Specifically, an impedance detection module is disposed in the NFCC, and the detection process of the impedance detection module includes two phases, as shown in fig. 2, where the first Phase is a Polling Phase (Polling Phase), and in this Phase, the impedance detection module outputs a Polling signal through a first output terminal TXP and a second output terminal TXN of the NFCC, and the second Phase is a Listening Phase (Listening Phase), and in this Phase, the impedance detection module detects an impedance change between the first output terminal TXP and the second output terminal TXN, and determines that the target device is detected when the degree of the impedance change exceeds a threshold. In the polling stage, the duration of the polling signal sent by the impedance detection module is tens of microseconds, the polling signal is composed of five types of NFC-ACM, NFC-A, NFC-B, NFC-F and NFC-V, which type of polling signal can be selected independently in actual use, and the more the types of polling signals are selected, the longer the duration of the polling signal is, and the more the types of NFC target devices can be detected. For example, in fig. 2, three types of polling signals of NFC-A, NFC-B, NFC-F are selected, and if more types of polling signals are selected, the duration of the polling signal will be longer, the longer the duration of the polling signal, the more average current is required by the NFCC during the detection process, and the more power is consumed, the more power consumption of the NFC device will be.

For this reason, the present application proposes an NFC device capable of realizing detection of a target device by the NFC device with relatively small power consumption.

The inventor finds that when other NFC devices approach the NFC antenna in the NFC device, the capacitance of the NFC antenna may increase, and based on this phenomenon, the NFC device in the embodiment of the present application realizes detection of the target device by detecting the change in capacitance of the NFC antenna. Specifically, a self-capacitance detection module for detecting the capacitance variation of the NFC antenna is arranged in the NFC equipment, and the capacitance detection end of the self-capacitance detection module is connected with the positive phase end or the negative phase end of the NFC antenna.

The implementation of the NFC device of the present application is illustrated below by means of embodiments.

Fig. 3 is a schematic structural diagram of an embodiment of an NFC device of the present application, as shown in fig. 3, where the NFC device includes: NFC antenna 21, self-capacitance detection module 22, NFCC23, matching module 24, filtering module 25.

The first output end TXP and the second output end TXN of the NFCC23 are respectively and correspondingly connected to the first end P251 and the second end P252 of the filtering module 25, the third end P253 and the fourth end P254 of the filtering module 25 are correspondingly connected to the first end P241 and the second end P242 of the matching module 24, the third end P243 of the matching module 24 is connected to the non-inverting end N1 of the NFC antenna 21, and the fourth end P244 of the matching module 24 is connected to the inverting end N2 of the NFC antenna 21;

the first end of the data interaction module 211 in the NFCC23 sequentially passes through the first receiving end RXP of the NFCC23 and the first data receiving branch to be connected with the normal phase end N1 of the NFC antenna 21, and the second end of the data interaction module 211 sequentially passes through the second receiving end RXN of the NFCC23 and the second data receiving branch 27 to be connected with the normal phase end N2 of the NFC antenna 21.

In fig. 3, the capacitance detection terminal P1 of the self-capacitance detection module 22 is directly connected to the normal phase terminal N1 of the NFC antenna 21, and detects the capacitance change amount in the NFC antenna 21.

In the embodiment of another NFC device provided in the present application, the capacitance detection end P1 of the self-capacitance detection module 22 may be directly connected to the inverting end N2 of the NFC antenna 21, at this time, the structure of the NFC device may refer to the NFC device shown in fig. 3, and the difference is only that the capacitance detection end P1 of the self-capacitance detection module 22 is directly connected to the inverting end N2 of the NFC antenna.

In the embodiment of another NFC device provided in the present application, the capacitance detection end P1 of the self-capacitance detection module 22 is connected to the normal phase end N1 or the reverse phase end N2 of the NFC antenna 21 through the matching module 24, which is different from the capacitance detection end P1 of the self-capacitance detection module 22 in the NFC device shown in fig. 3. Specifically, the capacitance detecting terminal P1 of the self-capacitance detecting module 22 may be connected to the first terminal P241 or the second terminal P242 of the matching module 24. At this time, the structure of the NFC device may refer to the NFC device shown in fig. 3, which is different only in that the capacitance detection terminal P1 of the self-capacitance detection module 22 is directly connected to the first terminal P241 or the second terminal P242 of the matching module 24.

In the NFC device of the foregoing embodiment, taking an example that the self-capacitance detection module 22 is located outside the NFCC as an example, in another embodiment of the NFC device provided in the present application, the self-capacitance detection module 22 in the foregoing embodiment may be located in the NFCC23, where the capacitance detection end P1 of the self-capacitance detection module 22 may be connected to a pin of the NFCC23, and the pin is connected to the non-inverting end N1 of the NFC antenna 21, or connected to the inverting end N2 of the NFC antenna, or connected to the first end P241 of the matching module 24, or connected to the second end P242 of the matching module 24.

In the embodiment of the NFC device provided in the present application, as shown in fig. 4, the capacitance detection end P1 of the self-capacitance detection module 22 is directly connected to the normal phase end N1 of the NFC antenna 21, and the self-capacitance detection module 22 is located outside the NFCC23, specifically, the capacitance detection end P1 of the self-capacitance detection module 22 is connected to the first end of the first data receiving branch 26, and the first end is the end of the first data receiving branch 26 connected to the first data receiving end RXP of the NFCC23, as shown in fig. 4.

In another embodiment of the NFC device provided in the present application, the capacitance detection terminal P1 of the self-capacitance detection module 22 is connected to the inverting terminal N2 of the NFC antenna 21 through the second data receiving branch 27, and the self-capacitance detection module 22 is located outside the NFCC 23. At this time, the structure of the NFC device may refer to the NFC device shown in fig. 4, which is different only in that the capacitance detecting terminal P1 of the self-capacitance detecting module 22 is connected to the first terminal of the second data receiving branch 27, and the first terminal is the terminal of the first data receiving branch 26 connected to the second data receiving terminal RXN of the NFCC 23.

In another embodiment of the NFC device provided in the present application, as shown in fig. 5, the self-capacitance detection module 22 may be located in the NFCC23, and the capacitance detection terminal P1 is connected to the first receiving terminal RXP of the NFCC23, unlike the NFC device shown in fig. 4, in which the self-capacitance detection module 22 is located outside the NFCC 23.

In another embodiment of the NFC device provided in the present application, the self-capacitance detection module 22 is located in the NFCC23, and the capacitance detection terminal P1 is connected to the second receiving terminal RXN of the NFCC23, where the NFC device structure may refer to the NFC device shown in fig. 5, and the difference is that the capacitance detection terminal P1 is connected to the second receiving terminal RXN of the NFCC 23.

For the NFC device in the above embodiment, after the self-capacitance detection module 22 detects that the capacitance of the NFC antenna 21 changes, that is, the target device is detected, the data interaction module 211 in the NFCC23 may acquire data in the target device through the NFC antenna 21, and simultaneously turn off the self-capacitance detection module 22. Specifically, a switch may be disposed at the capacitance detection end P1 of the self-capacitance detection module 22, and configured to be turned on when the self-capacitance detection module 22 is required to detect the target device, so that the self-capacitance detection module 22 works, and turned off after the self-capacitance detection module 22 detects the target device, so that the self-capacitance detection module 22 pauses to work, thereby reducing the influence or interference of the self-capacitance detection module 22 on the module or circuit involved in NFC data interaction, such as the data interaction module 211, in the NFC device.

For similar reasons, in order to prevent the signals output by other modules from affecting the operation of the self-capacitance detection module 22, a switch for controlling whether the modules operate may be provided for other modules, and the switch may be turned on when the corresponding module needs to operate, so that the corresponding module is powered on and turned off when the corresponding module does not need to operate, so that the corresponding module is suspended.

Taking the NFC device shown in fig. 5 as an example, a switch for controlling whether the capacitive detection module 22 and the data interaction module 211 operate may be respectively provided for the capacitive detection module 22 and the data interaction module 211, as shown in fig. 6, different from the NFC device shown in fig. 5, a first switch K1 is provided between a first input end RXP of the NFCC23 and a capacitive detection end P1 of the self-capacitive detection module 22, a second switch K2 is provided between a first input end RXP of the NFCC23 and a first end P1 of the data interaction module 211, and a third switch K3 is provided between a second input end RXN of the NFCC23 and a second end P2 of the data interaction module 211; therefore, when the target device is detected, the NFC device may control the first switch K1 to be turned on, the second switch K2 and the third switch K3 to be turned off, so that the data interaction module 211 pauses the operation, the self-capacitance detection module 23 detects whether the capacitance of the NFC antenna 21 changes to detect the target device, once the self-capacitance detection module 23 detects the target device, the NFC device may control the first switch K1 to be turned off, the second switch K2 and the third switch K3 to be turned on, so that the self-capacitance detection module 23 pauses the operation, and the data interaction module 211 reads the data in the target device through the NFC antenna 21.

Since the matching module 24, the filtering module 25, and other modules of the NFC device may be provided with a capacitor, when the self-capacitance detection module 22 in the above embodiment works, the equivalent circuit between the capacitance detection end P1 and the power ground GND of the self-capacitance detection module 22 may include not only the capacitance of the NFC antenna, but also the capacitance in the matching module 24 and the filtering module 25, that is, the equivalent capacitance of the external circuit between the capacitance detection end P1 of the self-capacitance detection module 22 and the power ground GND is not only the capacitance of the NFC antenna, and since only the capacitance of the NFC antenna changes when the target device approaches, even if the self-capacitance detection module 22 detects the equivalent capacitance of the external circuit including the capacitance of the NFC antenna, the change of the capacitance of the NFC antenna can still be detected. However, if the capacitance value of the capacitor included in the matching module 24, the filtering module 25, or the like is relatively large, and the capacitance variation of the NFC antenna caused by the approach of the target device is relatively small, the capacitor included in the matching module 24, the filtering module 25, or the like may cause a decrease in the detection accuracy of the capacitance variation of the self-capacitance detection module 22 with respect to the NFC antenna, that is, a decrease in the detection accuracy of the NFC device with respect to the target device. For this reason, when the self-capacitance detection module 22 works, for a capacitor with one end grounded in the matching module 24, the filtering module 25 and other modules, the connection between the capacitor and the power ground GND can be disconnected, so as to improve the detection precision of the self-capacitance detection module 22, however, other modules may exist in the NFC device and need the capacitor to be grounded to work normally, so in another embodiment of the NFC device provided in the application, if the circuit of the NFC device, for example, the circuit of the matching module 24, the filtering module 25 and other modules includes a capacitor with a grounding end, the grounding end of the capacitor refers to one end of the capacitor connected to the power ground GND, a switch can be set between the grounding end of the capacitor and the power ground GND, and is used to turn off when the self-capacitance detection module 22 works, so as to turn off the connection between the grounding end of the corresponding capacitor and the power ground GND, thereby reducing the influence of the capacitor in the NFC circuit on the detection precision of the self-capacitance detection module 22, and is also used to pause the self-capacitance detection module 22, while the other modules in the NFC device work, so as to turn on when the other modules work, so as to ensure that the connection between the grounding end of the capacitor and the other modules is connected to the ground.

For similar reasons, in order to reduce the influence of the capacitor in the NFC device circuit on the detection precision of the self-capacitance detection module and ensure the normal operation of other modules, the first output terminal TXP and the second output terminal TXN of the NFCC23 may be respectively grounded through switches, and accordingly, when the self-capacitance detection module 22 works, the NFC device controls the switches corresponding to the first output terminal TXP and the second output terminal TXN to be respectively turned off, and when the self-capacitance detection module 22 pauses the work and other modules, such as the data interaction module 211, the NFC device controls the switches corresponding to the first output terminal TXP and the second output terminal TXN to be respectively turned on, so as to ensure the normal operation of other modules.

The implementation principle of the above embodiment is illustrated by the following specific examples:

referring to fig. 7, a possible circuit implementation structure of the matching module 24, the filtering module 25, the first data receiving branch 26 and the second data receiving branch 27 is given based on the embodiment shown in fig. 6, and an equivalent circuit structure of the NFC antenna 21 is given for convenience of explanation.

The matching module 24 is implemented by a symmetrical circuit structure, specifically, a first end P241 of the matching module 24 is connected to a third end P243 through a first capacitor C1, the third end P243 is grounded through a second capacitor C2, a second end P242 is connected to a fourth end P244 through a third capacitor C3, the fourth end P244 is further grounded through a fourth capacitor C4, and both the second capacitor C2 and the fourth capacitor C4 have grounding ends, that is, one end is connected to a power ground GND.

The filtering module 25 is implemented by a symmetrical circuit structure, the first end P251 is connected to the third end P253 through the first inductor L1, the third end P253 is further grounded through the fifth capacitor C5, the second end P252 is connected to the fourth end P254 through the second inductor L2, and the fourth end P254 is further grounded through the sixth capacitor C6; the fifth capacitor C5 and the sixth capacitor C6 each have a ground terminal.

The first data receiving branch 26 comprises a first resistor R1 and a seventh capacitor C7 in series, and the second data receiving branch 27 comprises a second resistor R2 and an eighth capacitor C8 in series.

The equivalent circuit structure of the NFC antenna 21 includes: the normal phase end N1 of the NFC antenna 21 is grounded through the first parasitic capacitor Ca1, the reverse phase end N2 is grounded through the second parasitic capacitor Ca2, the normal phase end N1 is further connected to the reverse phase end N2 through the coil resistor Ra, the first coil inductor La1 and the second coil inductor La2, and the capacitor Δc is the capacitance variation of the NFC antenna when the target device approaches.

When the self-capacitance detection module 22 performs capacitance detection, the capacitance detection terminal P1 may output a driving signal to an external circuit, and then determine the variation of the equivalent capacitance of the external circuit between the capacitance detection terminal P1 and the power ground GND according to the signal detected by the capacitance detection terminal P1. In general, the detection frequency of the self-capacitance detection module is between 10kHZ and 2MHZ, and at this time, when the self-capacitance detection module 22 outputs a driving signal to the NFC antenna, the impedance of the NFC antenna is close to 0, that is, ra is close to 0, so that when the self-capacitance detection module works, the coil of the NFC antenna is considered to be a wire, that is, the coil resistor Ra, the first coil inductance La1 and the second coil inductance La2 are equivalent to be a wire; at this time, if the first switch K1 is closed and the second switch K2 and the third switch K3 are opened in the circuit shown in fig. 7, the equivalent circuit is shown in fig. 8, in which only the capacitance Δc changes when the target device approaches the NFC antenna, so that the self-capacitance detection module 22 can realize the detection of the target device by detecting the change amount of the equivalent capacitance of the external circuit between the capacitance detection terminal P1 of the self-capacitance detection module 22 and the power ground GND, in fig. 7, that is, the external circuit between the first receiving terminal RXP of the NFCC23 and the power ground GND, the equivalent capacitance of the external circuit is the parallel capacitance of the 4 branches of the second capacitance C2, the first capacitance C1 and the fifth capacitance C5 connected in series, the first parasitic capacitance Ca1, and the capacitance Δc.

In addition, in fig. 8, the seventh capacitor C7 is generally a blocking capacitor, and the capacitance value is generally much larger than the capacitance values of the first capacitor C1 to the sixth capacitor C6, so that the influence on the capacitance detection of the self-capacitance detection module 22 is small, but the first capacitor C1, the fifth capacitor C5 and the second capacitor C2 connected in series will influence the capacitance detection of the self-capacitance detection module 22, specifically, the equivalent capacitance after the parallel connection of the 2 branches is assumed to be Ce1, and then the equivalent capacitance Ce1 is connected in parallel with the first parasitic capacitor Ca1 and the capacitor Δc, so that the capacitance value detected by the self-capacitance detection module 22 becomes small, that is, the variation of the detected capacitance value becomes small, and the detection accuracy of the self-capacitance detection module 22 is affected.

For this reason, unlike the NFC device shown in fig. 7, the fourth switch K4 is provided in the NFC device shown in fig. 9, and the grounding terminal of the second capacitor C2, the fourth capacitor C4, the fifth capacitor C5, and the sixth capacitor C6 is controlled to be grounded by the switching state of the fourth switch K4. Specifically, when the self-capacitance detection module 22 works, the fourth switch K4 may be controlled to be turned off, and at this time, as shown in fig. 10, the equivalent circuit of the NFC device shown in fig. 9, compared with the equivalent circuit shown in fig. 8, the first capacitor C1, the second capacitor C2, and the fifth capacitor C5 will not affect the capacitance variation detected by the self-capacitance detection module 22, so as to improve the detection accuracy of the self-capacitance detection module 22.

While ensuring the detection precision of the self-capacitance detection module 22, when the self-capacitance detection module 22 does not need to work, but other modules work, for example, when the data interaction module 211 starts to work after the self-capacitance detection module 22 detects the target device, the fourth switch K4 can be turned on to ensure the normal work of the data interaction module 211.

For similar reasons, in order to reduce the influence of the capacitance in the NFC device circuit on the detection accuracy of the self-capacitance detection module 22 and ensure the normal operation of other modules, as shown in fig. 11, the first output terminal TXP and the second output terminal TXN of the NFCC23 may be respectively grounded through the fifth switch K5 and the sixth switch K6, and accordingly, when the self-capacitance detection module 22 works, the fifth switch K5 and the sixth switch K6 are turned off, and when the self-capacitance detection module 22 pauses working, the fifth switch K5 and the sixth switch K6 are turned on. Alternatively, as shown in fig. 11, a branch circuit grounded to the fourth switch K4 may be disposed inside the NFCC, so as to control the fourth switch K4. It should be noted that, whether the fourth switch K4, the fifth switch K5, and the sixth switch K6 are turned on or off when the self-capacitance detection module 22 is operated is related to the actual circuit structure of the NFC device, and the principle of reducing the parallel capacitance of the capacitor Δc is taken as a principle. For example, for the NFC device shown in fig. 9 and 11, when the self-capacitance detection module 22 is operated, if the fourth switch K4, the fifth switch K5, and the sixth switch K6 are turned off, the influence on the detection accuracy of the self-capacitance detection module is minimal, but when the fourth switch K4, the fifth switch K5, and the sixth switch K6 are turned on, the self-capacitance detection module can still realize the capacitance detection. However, for example, as shown in fig. 12, the capacitance detection end of the self-capacitance detection module 22 is connected to the first end P241 of the matching circuit 24 through the first data receiving branch 26, and then is connected to the normal phase end N1 of the NFC antenna 21 through the matching circuit, at this time, the equivalent circuit of fig. 12 is shown in fig. 13, and when the fourth switch K4, the fifth switch K5, and the sixth switch K6 are turned off, the influence of the capacitance in the circuit on the detection accuracy of the self-capacitance detection module is minimal, and it should be noted that the fifth switch K5 must be turned off to ensure that the self-capacitance detection module can implement the capacitance detection of the NFC antenna.

Alternatively, the self-capacitance detection module 23 in the above-described embodiment may be implemented by a self-capacitance detection circuit shown in fig. 14, for example, which includes:

the capacitance detection end P1 of the self-capacitance detection module 22 is connected with the power supply voltage end VCC through a seventh switch K7, grounded through an eighth switch K8, connected with the non-inverting input end of the differential amplifier A1 through a ninth switch K9, connected with the first end of a ninth capacitor C9 through a tenth switch K10, and grounded through the second end of the ninth capacitor C9;

the first end of the ninth capacitor C9 is further connected to the power supply voltage end VCC through an eleventh switch K11, and is grounded through a twelfth switch K12;

the inverting input terminal of the differential amplifier A1 is connected to the common-mode voltage terminal VCM, and the first output terminal and the second output terminal are configured to output a detected voltage, where the detected voltage is positively correlated with the capacitance of the NFC antenna.

The non-inverting input end of the differential amplifier A1 is also connected with the first output end of the differential amplifier A1 through a third resistor R3 and a tenth capacitor C10 which are connected in parallel, and the inverting input end is connected with the second output end of the differential amplifier A1 through a fourth resistor R4 and an eleventh capacitor C11 which are connected in parallel.

Alternatively, the non-inverting input terminal of the differential amplifier A1 may also be connected to the first output terminal of the differential amplifier A1 only through the third resistor R3 or the tenth capacitor C10; the inverting input terminal of the differential amplifier A1 may also be connected to the second output terminal of the differential amplifier A1 only through the fourth resistor R4 or the eleventh capacitor C11.

The self-capacitance detection circuit shown in fig. 14 is a self-capacitance detection scheme for charge transfer. The capacitance value of the ninth capacitor C9 in the circuit may be equal to the equivalent capacitance of the external circuit between the capacitance detection terminal P1 and the power ground terminal when no target device is approaching, for example, the equivalent capacitance of the external circuit in fig. 10 is the first parasitic capacitance Ca1, and the voltage of the common-mode voltage terminal VCM in the circuit may be Vcc/2.

Fig. 15 is a timing chart of the operation of the self-capacitance detection circuit shown in fig. 14, in which the control switch is turned on when the control signal is at a high level and the control switch is turned off when the control signal is at a low level. As shown in fig. 15, each of the duty cycles Tcds of the circuit can be divided into six time periods in total: in the period T1, only the seventh switch K7 and the twelfth switch K12 are turned on, and the other switches are turned off, at this time, the power supply voltage terminal VCC charges a capacitor (hereinafter simply referred to as an external capacitor) of the external circuit of the self-capacitance detection module 22 through the eighth switch K8, the voltage of the capacitance detection terminal P1 increases to the power supply voltage, and at the same time, both ends of the ninth capacitor C9 are grounded, the ninth capacitor C9 discharges, the voltage at the point N3 in fig. 14 is 0, the non-inverting input terminal of the differential amplifier A1 has no signal, and the output voltage VOUT is 0; in the period of T2, only the tenth switch K10 is conducted, the external capacitor and the ninth capacitor C9 are connected in parallel, charges of the two capacitors are mutually transferred, if the external non-target device is close to the NFC antenna, as the capacitance values of the external capacitor and the ninth capacitor are the same, the voltage of the ninth capacitor C9 is Vcc/2, the non-inverting input end of the differential amplifier A1 has no signal, and the output voltage VOUT is 0; in the period T3, only the ninth switch K9 and the tenth switch K10 are turned on, if no target device approaches the NFC antenna, the capacitance value of the external capacitor is unchanged, and the voltage of the ninth capacitor C9 is still Vcc/2, so that the voltage of the non-inverting input terminal of the differential amplifier A1 is Vcc/2, which is equal to the voltage of the common-mode voltage terminal VCM connected to the inverting input terminal, the output voltage VOUT of the differential amplifier A1 is still 0 (shown by the dashed line in fig. 15), if there is a target device approaching the NFC antenna, the NFC antenna generates a capacitance change, and the charge amount of q1= Δc (Vcc/2) is transferred to the non-inverting input terminal of the differential amplifier A1, and the output voltage VOUT of the differential amplifier A1 generates a waveform with the highest voltage U1; in the period of T4, only the eighth switch K8 and the eleventh switch K11 are conducted, the power supply voltage end VCC charges the ninth capacitor C9 through the eleventh switch K11, the voltage of the N3 point is increased to the power supply voltage, the external capacitor discharges through the eighth switch K8, the voltage of the capacitor detection end P1 is 0, no signal exists at the non-inverting input end of the differential amplifier A1 due to the disconnection of the ninth switch K9, and the output voltage VOUT is 0; in the period of T5, only the tenth switch K10 is conducted, the external capacitor and the ninth capacitor C9 are connected in parallel, charges of the two capacitors are mutually transferred, and if no target equipment is close to the NFC antenna, the capacitance values of the external capacitor and the ninth capacitor are the same, and at the moment, the capacitance voltage of the ninth capacitor is Vcc/2; in the period T6, only the ninth switch K9 and the tenth switch K10 are turned on, if no target device is close to the NFC antenna, the capacitance value of the external capacitor is unchanged, the capacitance voltage of the ninth capacitor C9 is still Vcc/2, so that the voltage of the non-inverting input terminal of the differential amplifier A1 is Vcc/2, the voltage equal to the voltage of the common-mode voltage terminal VCM to which the inverting input terminal is connected, the output voltage VOUT of the differential amplifier A1 is still 0 (shown by the dashed line in fig. 15), if there is a target device close to the NFC antenna, the NFC antenna generates a capacitance change, and the charge amount of q2= - Δc1/2 Vcc is transferred to the non-inverting input terminal of the differential amplifier A1, and the output voltage VOUT of the differential amplifier A1 generates a waveform with a minimum voltage of-U1. By demodulating the output voltage VOUT of the differential amplifier A1, the amount of change Δc in the external capacitance can be detected based on the demodulated information, thereby knowing whether the target device is detected.

The output terminal of the self-capacitance detection module 22 in the above embodiment may output the first signal generated based on the detected capacitance variation amount of the NFC antenna, for example, when the self-capacitance detection module 22 is implemented by the self-capacitance detection circuit shown in fig. 14, the first signal generated by the self-capacitance detection module 22 is the voltage signal VOUT.

In another embodiment of the NFC device provided in the present application, the NFC device of the foregoing embodiment may further include: the input end of the judging module can be connected with the output end of the self-capacitance detecting module 22, and the judging module is used for receiving the first signal output by the self-capacitance detecting module 22, judging whether the amplitude of the first signal exceeds a preset threshold value, if so, judging that the target equipment is close to the NFC antenna, otherwise, judging that no target equipment is close to the NFC antenna. The specific value of the preset threshold is not limited in this embodiment, and is related to the first signal generated by the self-capacitance detection module 22. The determining module may be disposed outside the NFCC23, or may be disposed in the NFCC 23. Referring to fig. 16, taking the NFC device addition determining module 28 shown in fig. 12 as an example, the determining module 28 is located in the NFCC.

Currently, an NFC device detects a target device by detecting the impedance of an NFC antenna, when a polling signal is sent, the driving voltage is generally 2-6V, the impedance of a driving circuit is generally 20 Ω -50Ω, then the driving current is greater than 100mA, assuming that the polling time is 30us, the power consumption of one polling is greater than j=2v×100ma=6x10e-6 joules, in the NFC device of the present invention, the target device is detected by detecting the capacitance of the NFC antenna, when the self-capacitance detection module works, the driving voltage may be 2-3.3V, the load capacitance may be 100-500 pF, assuming that the working frequency is 100kHz, the polling time is 200us, then the driving current i=100khz×2pf=20ua, and the power consumption of one polling j=2v×20ua=8x10e-9 joules. Compared with the NFC antenna, the NFC device detects the target device in a mode of detecting the capacitance of the NFC antenna, and has obvious advantages in power consumption.

In the embodiments of the present application, "at least one" means one or more, and "a plurality" means two or more. "and/or", describes an association relation of association objects, and indicates that there may be three kinds of relations, for example, a and/or B, and may indicate that a alone exists, a and B together, and B alone exists. Wherein A, B may be singular or plural. The character "/" generally indicates that the context-dependent object is an "or" relationship. "at least one of the following" and the like means any combination of these items, including any combination of single or plural items. For example, at least one of a, b and c may represent: a, b, c, a and b, a and c, b and c or a and b and c, wherein a, b and c can be single or multiple.

Those of ordinary skill in the art will appreciate that the various modules and algorithm steps described in the embodiments disclosed herein can be implemented as a combination of electronic hardware, computer software, and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.

It will be clearly understood by those skilled in the art that, for convenience and brevity of description, specific working procedures of the above-described system, apparatus and module may refer to corresponding procedures in the foregoing method embodiments, which are not repeated herein.

In several embodiments provided herein, any of the functions, if implemented in the form of software functional modules and sold or used as a stand-alone product, may be stored on a computer-readable storage medium. Based on such understanding, the technical solution of the present application may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution, in the form of a software product stored in a storage medium, including several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in the embodiments of the present application. And the aforementioned storage medium includes: a usb disk, a removable hard disk, a Read-Only Memory (hereinafter referred to as ROM), a random access Memory (Random Access Memory) and various media capable of storing program codes such as a magnetic disk or an optical disk.

The foregoing is merely specific embodiments of the present application, and any person skilled in the art may easily conceive of changes or substitutions within the technical scope of the present application, which should be covered by the protection scope of the present application. The protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A near field communication, NFC, device, the NFC device comprising: the NFC antenna, be used for carrying out signal filtering's filter circuit, be used for carrying out NFC antenna impedance match's matching circuit, be used for transmitting the data signal's that NFC antenna received data receiving branch road, be used for control signal transmission and receiving's NFC controller, its characterized in that, NFC equipment still includes: a self-capacitance detection module, wherein,

the self-capacitance detection module is used for detecting the capacitance variation of the NFC antenna and judging whether target equipment is close to the NFC antenna or not;

the self-capacitance detection module is positioned in the NFC controller;

the grounding ends of the capacitors included in the matching circuit and the filter circuit are grounded through a switch, and the switch is used for being turned off when the self-capacitance detection module works.

2. The device of claim 1, wherein a capacitance detection terminal of the self-capacitance detection module is connected to a positive or negative terminal of the NFC antenna through the matching circuit.

3. The device of claim 1, wherein a capacitance detection end of the self-capacitance detection module is connected to a positive phase end or a negative phase end of the NFC antenna through the data receiving branch.

4. The device of claim 1, wherein a capacitance detection end of the self-capacitance detection module is connected to a positive phase end or a negative phase end of the NFC antenna sequentially through the data receiving branch and the matching circuit.

5. The apparatus of any one of claims 1 to 4, wherein a capacitance detection terminal of the self-capacitance detection module is connected to a first terminal of a first switch, a second terminal of the first switch is connected to a positive terminal or a negative terminal of the NFC antenna, the first switch is configured to be turned on when the self-capacitance detection module is in operation, and turned off when the self-capacitance detection module is not in operation.

6. The apparatus of any one of claims 1 to 4, wherein the self-capacitance detection module comprises a seventh switch, an eighth switch, a ninth switch, a tenth switch, an eleventh switch, a twelfth switch, a differential amplifier, and a ninth capacitance, the self-capacitance detection module further comprising: a third resistor and/or a tenth capacitor, a fourth resistor and/or an eleventh capacitor, wherein,

7. The device of claim 6, wherein the ninth capacitance has a capacitance value equal to a first equivalent capacitance value, the first equivalent capacitance value being an equivalent capacitance value of an external circuit of the self-capacitance detection module between the capacitance detection terminal and a power ground terminal when no target device is near the NFC antenna, the voltage of the common mode voltage terminal being 1/2 of the power supply voltage.

8. The apparatus according to any one of claims 1 to 4, wherein the self-capacitance detection module is specifically configured to: generating a first signal based on the detected capacitance variation of the NFC antenna;

the NFC device further includes: the judging module is used for judging whether the amplitude of the first signal output by the self-capacitance detection module exceeds a preset threshold value or not, and if so, judging that the target equipment is close to the NFC antenna.

9. The apparatus according to any one of claims 1 to 4, wherein the NFC controller is configured to determine whether or not a target apparatus is close to the NFC antenna according to the capacitance change amount.