CN114097180A

CN114097180A - NFC equipment

Info

Publication number: CN114097180A
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: 2022-02-25
Anticipated expiration: 2040-12-28
Also published as: WO2022140957A1; CN114097180B

Abstract

The application provides an NFC equipment, NFC equipment includes filter circuit, matching circuit, data reception branch road, NFC controller and NFC antenna, still includes: the self-capacitance detection module, wherein, the positive phase end or the negative phase end of NFC antenna are connected to self-capacitance detection module's electric capacity detection terminal, and self-capacitance detection module is used for detecting the electric capacity variation of NFC antenna. The NFC device can achieve detection of the target device through relatively low power consumption.

Description

NFC equipment

Technical Field

The application relates to the field of NFC communication, in particular to an NFC device.

Background

When Near Field Communication (NFC) devices are used as initiating devices in NFC Communication, target devices need to be detected based on NFC antennas, and the target devices are also NFC devices. The current detection method is as follows: an impedance detection module is arranged in an NFC controller (NFCC) of NFC equipment, a polling signal with duration of dozens of microseconds is 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, target equipment exists in the environment.

However, the target device detection method causes the NFC device to consume more power.

Disclosure of Invention

The application provides an NFC device, which can detect a target device through relatively low 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 equipment comprises an NFC antenna, a filter circuit for filtering signals, a matching circuit for matching impedance of the NFC antenna, a data receiving branch for transmitting data signals received by the NFC antenna, and an NFC controller for controlling signal sending and receiving, and further comprises: the self-capacitance detection module, wherein, self-capacitance detection module's electric capacity detection end is connected the normal phase end or the inverting terminal of NFC antenna, self-capacitance detection module is used for detecting the electric capacity variation of NFC antenna, electric capacity variation is used for judging whether there is target equipment to be close to the NFC antenna.

This NFC equipment has realized the detection to target device through the mode that self-capacitance detection module detected the electric capacity change volume of NFC antenna, moreover, for the mode that impedance detection module carries out target device detection at every turn and sends the polling signal that duration is tens of microseconds among the prior art, self-capacitance detection module has less consumption relatively.

In a 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 a 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 a possible implementation manner, 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.

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

In a possible implementation manner, a 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 configured to be 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 a possible implementation manner, the NFC device includes a matching circuit and a filter circuit of the NFC antenna, ground terminals of capacitors included in the matching circuit and the filter circuit are grounded through a fourth switch, and the fourth switch is configured to be turned off when the self-capacitance detection module operates.

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

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

the first end of the ninth capacitor is also connected with a power supply voltage end through an eleventh switch and is 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 positive phase input end of the differential amplifier is also connected with the first output end of the differential amplifier through a third resistor, a tenth capacitor, or a third resistor and a tenth capacitor which are connected in parallel, and the negative phase input end of the differential amplifier is connected with the second output end of the differential amplifier through a fourth resistor, an eleventh capacitor, or a fourth resistor and an eleventh capacitor which are connected in parallel.

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

In a 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 input end of the judgment module is connected with the output end of the self-capacitance detection module, the judgment 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, a target device is judged to be close to the NFC antenna, and otherwise, no target device is judged to be close to the NFC antenna.

In a 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 needed to be used 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 it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic 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 an embodiment of an NFC device according to the present application;

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

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

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

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

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

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

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

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

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

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

FIG. 14 is a schematic structural diagram of an 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 detection circuit shown in FIG. 14 according to the present application;

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

Detailed Description

The terminology used in the description of the embodiments 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.

Generally, the NFC device structure is shown in fig. 1, and includes: NFCC, NFC antenna, matching module and filtering module. The filtering module may be configured to filter a signal, the matching module may be configured to perform impedance matching of the NFC antenna, and the NFCC may be configured to control signal transmission and reception, where signals transmitted and received by the NFCC are generally signals related to an NFC communication protocol. The NFC communication protocol may be an NCI 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 may be connected to a first receiving terminal RXP and a second receiving terminal RXN of the NFCC, respectively, and then connected to two ends of the NFC antenna through a first data transmission branch and a second data transmission branch, respectively, so as to obtain a data signal received by the NFC antenna.

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

Therefore, the application provides the NFC device, which can detect the target device through the NFC device with relatively low 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 detects the target device by detecting the change in the 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 device, and 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.

The following is an exemplary description of an implementation of the NFC device of the present application by way of an embodiment.

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

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

a first end of the data interaction module 211 in the NFCC23 sequentially passes through the first receiving terminal RXP of the NFCC23 and the first data receiving branch to be connected to the positive phase terminal N1 of the NFC antenna 21, and a second end of the data interaction module 211 sequentially passes through the second receiving terminal RXN of the NFCC23 and the second data receiving branch 27 to be connected to the negative phase terminal 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 non-inverting terminal N1 of the NFC antenna 21, so as to detect the capacitance variation of the NFC antenna 21.

In contrast to the NFC device shown in fig. 3 in which the capacitance detection terminal P1 of the self-capacitance detection module 22 is directly connected to the non-inverting terminal N1 of the NFC antenna 21, in another embodiment of the NFC device provided in this application, the capacitance detection terminal P1 of the self-capacitance detection module 22 may be directly connected to the inverting terminal 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 terminal P1 of the self-capacitance detection module 22 is directly connected to the inverting terminal N2 of the NFC antenna.

Unlike the NFC device shown in fig. 3 in which the capacitance detection terminal P1 of the self-capacitance detection module 22 is directly connected to the positive terminal N1 of the NFC antenna 21, in another embodiment of the NFC device provided in this application, the capacitance detection terminal P1 of the self-capacitance detection module 22 is connected to the positive terminal N1 or the negative terminal N2 of the NFC antenna 21 through the matching module 24. Specifically, the capacitance detection terminal P1 of the self capacitance detection 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, and the only difference is 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 above embodiment, taking the self-capacitance detecting module 22 located outside the NFCC as an example, in another embodiment of the NFC device provided in this application, the self-capacitance detecting module 22 in the above embodiment may be located in the NFCC23, at this time, the capacitance detecting terminal P1 of the self-capacitance detecting module 22 may be connected to a pin of the NFCC23, where the pin is connected to the positive terminal N1 of the NFC antenna 21, or connected to the negative terminal N2 of the NFC antenna, or connected to the first terminal P241 of the matching module 24, or connected to the second terminal P242 of the matching module 24.

In contrast to the NFC device shown in fig. 3 in which the capacitance detection terminal P1 of the self-capacitance detection module 22 is directly connected to the positive phase terminal N1 of the NFC antenna 21, in another embodiment of the NFC device provided in this application, referring to fig. 4, the capacitance detection terminal P1 of the self-capacitance detection module 22 is connected to the positive phase terminal N1 of the NFC antenna 21 through the first data receiving branch 26, and the self-capacitance detection module 22 is located outside the NFCC23, specifically, the capacitance detection terminal P1 of the self-capacitance detection module 22 is connected to a first terminal of the first data receiving branch 26, where the first terminal is a terminal at which the first data receiving branch 26 is connected to the first data receiving terminal RXP of the NFCC 23.

In another embodiment of the NFC device provided in this 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, and only differ in that the capacitance detection terminal P1 of the self-capacitance detection module 22 is connected to the first terminal of the second data receiving branch 27, which is the terminal of the first data receiving branch 26 connected to the second data receiving terminal RXN of the NFCC 23.

Unlike the NFC device shown in fig. 4 in which the self-capacitance detection module 22 is located outside the NFCC23, in another embodiment of the NFC device provided in this application, referring to 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 NFCC 23.

In another embodiment of the NFC apparatus 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, at this time, the structure of the NFC apparatus may refer to the NFC apparatus shown in fig. 5, except 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 turn off the self-capacitance detection module 22 at the same time. Specifically, a switch may be disposed at the capacitance detection terminal P1 of the self-capacitance detection module 22, and is configured to be turned on when the self-capacitance detection module 22 is required to detect a target device, so that the self-capacitance detection module 22 operates, and is turned off after the self-capacitance detection module 22 detects the target device, so that the self-capacitance detection module 22 suspends operation, and thus, influence or interference of the self-capacitance detection module 22 on modules or circuits related to NFC data interaction, such as the data interaction module 211, in the NFC device is reduced.

For similar reasons, in order to prevent 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 the other modules, and the switch is turned on when the corresponding modules operate, so that the corresponding modules are powered on to operate, and turned off when the corresponding modules do not operate, so that the corresponding modules suspend operation.

Taking the NFC device shown in fig. 5 as an example, switches for controlling whether the capacitance detection module 22 and the data interaction module 211 operate or not may be respectively provided, as shown in fig. 6, different from the NFC device shown in fig. 5, a first switch K1 is provided between the first input terminal RXP of the NFCC23 and the capacitance detection terminal P1 of the self-capacitance detection module 22, a second switch K2 is provided between the first input terminal RXP of the NFCC23 and the first terminal P1 of the data interaction module 211, and a third switch K3 is provided between the second input terminal RXN of the NFCC23 and the second terminal P2 of the data interaction module 211; therefore, when target device detection is required, 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 suspends operation, the self-capacitance detection module 23 detects whether the capacitance of the NFC antenna 21 changes to detect the target device, once the target device is detected by the self-capacitance detection module 23, 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 suspends operation, and the data interaction module 211 reads 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 capacitors, for the self-capacitance detecting module 22 in the above embodiment, when the self-capacitance detecting module 22 operates, the equivalent circuit between the capacitance detecting terminal P1 and the power ground GND may not only include the capacitor of the NFC antenna, but also may include capacitors in the matching module 24 and the filtering module 25, that is, the equivalent capacitor of the external circuit between the capacitance detecting terminal P1 of the self-capacitance detecting module 22 and the power ground GND is not only the capacitor of the NFC antenna, and since only the capacitor of the NFC antenna changes when the target device approaches, even if the self-capacitance detecting module 22 detects the equivalent capacitor of the external circuit including the capacitor of the NFC antenna, the change condition of the capacitor of the NFC antenna can still be detected. However, if the capacitance values of the capacitors included in the modules such as the matching module 24 and the filtering module 25 are relatively large, and the capacitance variation of the NFC antenna caused by the approach of the target device is relatively small, then the capacitors included in the modules such as the matching module 24 and the filtering module 25 may cause the detection accuracy of the self-capacitance detecting module 22 for the capacitance variation of the NFC antenna to decrease, that is, the detection accuracy of the NFC device for the target device to decrease. For this reason, when the self-capacitance detection module 22 works, the capacitor with one grounded end existing in the matching module 24, the filtering module 25, and the like may be disconnected from the power ground GND, so as to improve the detection accuracy of the self-capacitance detection module 22, however, other modules may also exist in the NFC device and need the capacitor to be grounded for normal work, for this reason, in another embodiment of the NFC device provided in this application, if the capacitor with the grounded end is included in the circuit of the NFC device, such as the matching module 24, the filtering module 25, and the like, and the grounded end of the capacitor refers to the end of the capacitor connected to the power ground GND, then a switch may be provided between the grounded end of the capacitor and the power ground GND, and the switch is used to turn off when the self-capacitance detection module 22 works, so as to turn off the connection between the grounded end of the corresponding capacitor and the power ground GND, thereby reduce the influence of electric capacity to self-capacitance detection module 22 detection precision among the NFC circuit, this switch still is used for from the work of capacitor detection module 22 pause work, and other module during operation in the NFC equipment switch on to switch on and correspond being connected between electric capacity and the power ground terminal GND, make the ground terminal ground connection of electric capacity, thereby guarantee the normal work of other modules.

Based on similar reasons, in order to reduce the influence of capacitance in the NFC device circuit on the detection precision of the self-capacitance detection module and ensure the normal operation of other modules, it may further be configured that the first output terminal TXP and the second output terminal TXN of the NFCC23 are grounded through switches, correspondingly, when the self-capacitance detection module 22 operates, the NFC device controls the switches corresponding to the first output terminal TXP and the second output terminal TXN to be turned off respectively, when the self-capacitance detection module 22 stops operating, and when other modules, such as the data interaction module 211, operate, the NFC device controls the switches corresponding to the first output terminal TXP and the second output terminal TXN to be turned on respectively, so as to ensure the normal operation of other modules.

The following illustrates the implementation principle of the above embodiments by 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 for convenience of description, an equivalent circuit structure of the NFC antenna 21 is given.

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

The filter module 25 is implemented by a symmetrical circuit structure, the first terminal P251 is connected to the third terminal P253 through a first inductor L1, the third terminal P253 is further grounded through a fifth capacitor C5, the second terminal P252 is connected to the fourth terminal P254 through a second inductor L2, and the fourth terminal P254 is further grounded through a 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 connected in series, and the second data receiving branch 27 comprises a second resistor R2 and an eighth capacitor C8 connected in series.

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

The self-capacitance detecting module 22 can output a driving signal from the capacitance detecting terminal P1 to an external circuit during capacitance detection, and then determine the variation of the equivalent capacitance of the external circuit between the capacitance detecting terminal P1 and the power ground GND according to the signal detected by the capacitance detecting terminal P1. Generally, 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, it can be considered that when the self-capacitance detection module works, a coil of the NFC antenna is a wire, that is, a coil resistor Ra, a first coil inductor La1, and a second coil inductor La2 are equivalent to 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 as shown in fig. 8, wherein only the capacitance Δ C changes when the target device approaches the NFC antenna, so that the self-capacitance detection module 22 can detect 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, the external circuit is the external circuit between the first receiving terminal RXP of the NFCC23 and the power ground GND, see fig. 8, and the equivalent capacitance of the external circuit is the parallel capacitance of the 4 branches including the second capacitor C2, the first capacitor C1 and the fifth capacitor C5 connected in series, the first parasitic capacitor Ca1, and the capacitance Δ C.

In addition, in fig. 8, the seventh capacitor C7 is generally a dc 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 capacitance detection of the self-capacitance detection module 22 is slightly affected, however, the first capacitor C1, the fifth capacitor C5 and the second capacitor C2 connected in series will affect the capacitance detection of the self-capacitance detection module 22, specifically, the equivalent capacitance after the 2 branches are connected in parallel is assumed to be Ce1, and then the equivalent capacitance Ce1 is connected in parallel with the first parasitic capacitance Ca1 and the capacitance Δ C, 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.

Therefore, unlike the NFC device shown in fig. 7, the NFC device shown in fig. 9 is provided with a fourth switch K4, and the switching state of the fourth switch K4 controls whether the ground terminals of the second capacitor C2, the fourth capacitor C4, the fifth capacitor C5, and the sixth capacitor C6 are grounded. Specifically, when the self-capacitance detection module 22 works, the fourth switch K4 may be controlled to be turned off, at this time, as shown in fig. 10, in 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 may 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.

When the detection accuracy of the self-capacitance detection module 22 is ensured, the self-capacitance detection module 22 does not need to work, and other modules work, for example, when the data interaction module 211 starts to work after the self-capacitance detection module 22 detects a target device, the fourth switch K4 may 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 grounded through the fifth switch K5 and the sixth switch K6, respectively, and accordingly, when the self-capacitance detection module 22 operates, the fifth switch K5 and the sixth switch K6 are turned off, and when the self-capacitance detection module 22 temporarily stops operating, the fifth switch K5 and the sixth switch K6 are turned on. Optionally, as shown in fig. 11, the grounded branch of the fourth switch K4 may also be disposed inside the NFCC, so as to facilitate the control of 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 during the operation of the self-capacitance detecting module 22 is related to the actual circuit structure of the NFC device, so as to reduce the parallel capacitance of the capacitor Δ C. For example, for the NFC device shown in fig. 9 and 11, when the self-capacitance detection module 22 is in operation, if the fourth switch K4, the fifth switch K5, and the sixth switch K6 are turned off, the detection accuracy of the self-capacitance detection module is minimally affected, 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 achieve capacitance detection. However, for example, as shown in fig. 12, the capacitance detection terminal of the self-capacitance detection module 22 is connected to the first terminal P241 of the matching circuit 24 through the first data receiving branch 26, and is further connected to the non-inverting terminal N1 of the NFC antenna 21 through the matching circuit, at this time, the equivalent circuit shown in fig. 12 is as 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 on the NFC antenna.

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

a capacitance detection end P1 of the self-capacitance detection module 22 is connected to the power supply voltage end VCC through a seventh switch K7, is grounded through an eighth switch K8, is connected to the non-inverting input end of the differential amplifier a1 through a ninth switch K9, is connected to a first end of a ninth capacitor C9 through a tenth switch K10, and is grounded to a second end of the ninth capacitor C9;

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

the inverting input end of the differential amplifier a1 is connected to the common-mode voltage end VCM, the first output end and the second output end are used for outputting the detected voltage, and the detected voltage is positively correlated to the capacitance of the NFC antenna.

The non-inverting input terminal of the differential amplifier a1 is further connected to the first output terminal of the differential amplifier a1 through a third resistor R3 and a tenth capacitor C10 connected in parallel, and the inverting input terminal is connected to the second output terminal of the differential amplifier a1 through a fourth resistor R4 and an eleventh capacitor C11 connected in parallel.

Alternatively, the non-inverting input terminal of the differential amplifier a1 may 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 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 when no target device is close to, for example, the equivalent capacitance of the external circuit in fig. 10 is the first parasitic capacitor Ca1, and the voltage of the common mode voltage terminal VCM in the circuit may be Vcc/2.

Fig. 15 is an operation timing chart 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 is turned off when the control signal is at a low level. As shown in fig. 15, each duty cycle Tcds of the circuit may be divided into six time periods in total: in a time 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, 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 capacitor detection terminal P1 rises to the power supply voltage, meanwhile, 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, no signal is sent to the non-inverting input terminal of the differential amplifier a1, and the output voltage VOUT is 0; in a time period of T2, only the tenth switch K10 is turned on, the external capacitor and the ninth capacitor C9 are connected in parallel, charges of the external capacitor and the ninth capacitor C9 are transferred to each other, if no external target device is close to the NFC antenna, since capacitance values of the external capacitor and the ninth capacitor are the same, a voltage of the ninth capacitor C9 is Vcc/2, no signal is provided at a non-inverting input terminal of the differential amplifier a1, and an output voltage VOUT is 0; in the time period T3, 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 voltage of the ninth capacitor C9 is still Vcc/2, so that the voltage at the positive input terminal of the differential amplifier a1 is Vcc/2, which is equal to the voltage at the common-mode voltage terminal VCM connected to the negative input terminal, the output voltage VOUT of the differential amplifier a1 is still 0 (shown by a dotted line in fig. 15), if a target device is close to the NFC antenna, the NFC antenna generates a capacitance change, an electric charge quantity of Q1 ═ Δ C (Vcc/2) is transferred to the positive 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 a time period T4, only the eighth switch K8 and the eleventh switch K11 are turned on, the power supply voltage terminal VCC charges the ninth capacitor C9 through the eleventh switch K11, the voltage at the point N3 rises to the power supply voltage, the external capacitor is discharged through the eighth switch K8, the voltage of the capacitor detection terminal P1 is 0, since the ninth switch K9 is turned off, the non-inverting input terminal of the differential amplifier a1 has no signal, and the output voltage VOUT is 0; in a time period of T5, only the tenth switch K10 is turned on, the external capacitor and the ninth capacitor C9 are connected in parallel, charges of the external capacitor and the ninth capacitor are mutually transferred, if no target device is close to the NFC antenna, capacitance values of the external capacitor and the ninth capacitor are the same, and at this time, the capacitor voltage of the ninth capacitor is Vcc/2; in the time 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 capacitor voltage of the ninth capacitor C9 is still Vcc/2, so that the voltage at the positive input terminal of the differential amplifier a1 is Vcc/2, which is equal to the voltage at the common-mode voltage terminal VCM connected to the negative input terminal, the output voltage VOUT of the differential amplifier a1 is still 0 (shown by a dotted line in fig. 15), if a target device is close to the NFC antenna, the NFC antenna generates a capacitance change, an electric charge quantity of Q2 ═ Δ C × 1/2Vcc is transferred to the positive input terminal of the differential amplifier a1, and the output voltage VOUT of the differential amplifier a1 generates a waveform with the lowest voltage of-U1. By demodulating the output voltage VOUT of the differential amplifier a1, the amount of change Δ C in the external capacitance can be detected based on the demodulated information, and it can be known whether or not the target device is detected.

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

In another embodiment of the NFC device provided in this application, the NFC device of the above embodiment may further include: and the input end of the judgment module can be connected with the output end of the self-capacitance detection module 22, the judgment module is used for receiving the first signal output by the self-capacitance detection module 22 and judging whether the amplitude of the first signal exceeds a preset threshold value, if so, a target device is judged to be close to the NFC antenna, and otherwise, no target device is judged to be 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 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 an impedance of an NFC antenna, when a polling signal is sent, a driving voltage is generally 2 to 6V, a driving circuit impedance is generally 20 Ω to 50 Ω, and then a driving current is greater than 100mA, and assuming that a polling time is 30us, power consumption of one polling is greater than 2V 100mA 30us 6 e 10 e-6J, whereas in the NFC device of the present invention, an NFC antenna capacitance is used to detect the target device, when a self-capacitance detection module operates, the driving voltage may be 2 to 3.3V, a load capacitance may be 100 to 500pF, and assuming that an operating frequency is 100kHz and a polling time is 200us, a driving current I is 100kHz 2 pF 100pF 20uA, and a power consumption of one polling J is 2V 20uA 200us 8 us 10 e-9J. The comparison shows that the NFC equipment detects the target equipment by detecting the NFC antenna capacitance, and has obvious advantages in power consumption.

In the embodiments of the present application, "at least one" means one or more, "a plurality" means two or more. "and/or" describes the association relationship of the associated objects, and means that there may be three relationships, for example, a and/or B, and may mean that a exists alone, a and B exist simultaneously, and B exists alone. Wherein A and B can be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship. "at least one of the following" and similar expressions refer to any combination of these items, including any combination of singular 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 connection with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or combinations of electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. 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 can be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working processes of the system, the apparatus and the module described above may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.

In the several embodiments provided in the present application, any function, if implemented in the form of a software functional module and sold or used as a separate product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application or portions thereof that substantially contribute to the prior art may be embodied in the form of a software product stored in a storage medium and including instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: a U disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.

The above description is only for the specific embodiments of the present application, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present disclosure, and all the changes or substitutions 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 equipment comprises an NFC antenna, a filter circuit for filtering signals, a matching circuit for matching impedance of the NFC antenna, a data receiving branch for transmitting data signals received by the NFC antenna, and an NFC controller for controlling signal sending and receiving, and is characterized in that the NFC equipment further comprises: a self-capacitance detection module, 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 self-capacitance detection module is used for detecting the capacitance variation of the NFC antenna, and the capacitance variation is used for judging whether target equipment is close to the NFC antenna.

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

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

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

5. The device of any of claims 1-4, wherein the self-capacitance detection module is located in the NFC controller.

6. The device according to any one of claims 1 to 5, 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 non-inverting terminal or an inverting terminal of the NFC antenna, the first switch is configured to be turned on when the self-capacitance detection module is in operation, and the self-capacitance detection module is turned off when the self-capacitance detection module is not in operation.

7. The device according to any of claims 1 to 6, characterized in that a matching circuit and a filtering circuit of the NFC antenna are included in the NFC device, and a ground terminal of a capacitor included in the matching circuit and the filtering circuit is grounded through a fourth switch, and the fourth switch is used for being turned off when the self-capacitance detection module is in operation.

8. The apparatus of any of claims 1 to 7, 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, and further comprises: a third resistor and/or a tenth capacitor, a fourth resistor and/or an eleventh capacitor, wherein,

9. The apparatus of claim 8, wherein the capacitance of the ninth capacitor is equal to a first equivalent capacitance value between the capacitor detection terminal and a power ground terminal of an external circuit of the self-capacitance detection module when no target device is close to the NFC antenna, and the voltage of the common mode voltage terminal is 1/2 times of the power voltage.

10. The device according to any one of claims 1 to 9, wherein the self-capacitance detection module is specifically configured to: generating a first signal based on the detected amount of capacitance change of the NFC antenna;

the NFC device further includes: the input end of the judgment module is connected with the output end of the self-capacitance detection module, the judgment module is used for judging whether the amplitude of the first signal output by the self-capacitance detection module exceeds a preset threshold value, and if yes, a target device is judged to be close to the NFC antenna.

11. The device according to any of claims 1 to 9, wherein the NFC controller is configured to determine whether a target device is close to the NFC antenna according to the capacitance variation.