CN113067604B - NFC access control circuit and NFC device - Google Patents

Abstract

The NFC access control circuit and the NFC device provided by the present invention include an NFC device, an NFC sensing module, a switch module, an access module and a control module. When the user does not need to use the NFC device, the switch module is disconnected because there is no high-level input. NFC sensor module and NFC device, NFC read-write device cannot access this NFC device. When the user needs to use the NFC device, he only needs to trigger the access module once, and the control module will output a high-level signal to the switch module to turn on the NFC sensing module and the NFC device, so that the NFC device can be accessed. In addition, after the user operation is completed and the NFC device leaves the NFC read-write device, the NFC sensor module and the NFC device are disconnected because the control module will no longer output a high-level signal to the switch module, so the NFC device cannot be accessed. It can be seen that the NFC access control circuit provided by the present invention is not only extremely convenient to operate, but also has no potential safety hazards.

Description

NFC access control circuit and NFC device

technical field

The present invention relates to the technical field of NFC communication, in particular to an NFC access control circuit and an NFC device.

Background technique

The NFC antenna in the existing NFC device is usually directly and electrically connected to the NFC device, so that as long as the NFC device and other NFC read-write devices are within the communication range, corresponding read-write operations can be performed. However, the direct electrical connection between the NFC antenna and the NFC device will cause the NFC device to be easily accessed by unauthorized NFC read-write devices, that is, the NFC device can easily be read by others through the NFC read-write device without the user's knowledge. For write operations, such as an electronic cash card carried by the user, if someone else places the NFC reader/writer close to where the user places the electronic cash card, the user's balance can be easily deducted without the user's knowledge. It can be seen that the existing NFC device can be directly accessed by the NFC reading and writing device, and there is a large security risk.

SUMMARY OF THE INVENTION

In view of the above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide an NFC access control circuit and an NFC device, aiming to solve the problem that the existing NFC device can be directly accessed by an NFC reading and writing device, which has a large security risk.

In a first aspect, an NFC access control circuit provided by the present invention is applied to an NFC device, and the NFC access control circuit includes an NFC device, an NFC sensing module, a switch module, an access module and a control module;

The NFC sensing module is electrically connected with the switch module, and the switch module is electrically connected with the NFC device; the NFC sensing module is also electrically connected with the access module, and the access module is electrically connected with the control module , the control module is electrically connected to the switch module;

The NFC sensing module is used to generate an induced current and output a DC voltage when the NFC device is close to the NFC reading and writing device;

The access module is configured to turn on the NFC sensing module and the control module only when in a triggered state to trigger the control module;

The control module is configured to output a high-level signal to the switch module after being triggered to trigger the switch module;

The switch module is used to turn on the NFC sensing module and the NFC device when triggered, so that the NFC device can be accessed by the NFC reading and writing device.

Further, the NFC sensing module includes an NFC antenna and a conversion circuit, the NFC antenna is electrically connected to the AC input end of the conversion circuit, and the DC output end of the conversion circuit is respectively connected to the access module and the control module. The power input end of the switch module is electrically connected to the power input end of the switch module, and the NFC antenna is also electrically connected to the switch module;

The NFC antenna is used to generate an AC output when the NFC device is close to the NFC read-write device; the conversion circuit is used to convert the AC output generated by the NFC antenna into a DC and output a DC voltage.

Still further, the conversion circuit includes a rectifier circuit and a voltage stabilizer circuit, the NFC antenna is electrically connected to the AC input end of the rectifier circuit, and the DC output end of the rectifier circuit is electrically connected to the voltage stabilizer circuit. the voltage regulator circuit is electrically connected to the access module, the power input terminal of the control module and the power input terminal of the switch module;

The rectifier circuit is used to rectify the AC output generated by the NFC antenna into a DC output; the voltage regulator circuit is used to limit and stabilize the DC output voltage of the rectifier circuit;

The rectifier circuit includes a first rectifier diode, a second rectifier diode, a third rectifier diode and a fourth rectifier diode;

The anode of the first rectifier diode is electrically connected to the negative stage of the third rectifier diode to serve as the first pin of the AC input end of the rectifier circuit;

The anode of the second rectifier diode is electrically connected to the negative stage of the fourth rectifier diode to serve as the second pin of the AC input end of the rectifier circuit;

The cathode of the first rectifier diode is electrically connected to the cathode of the second rectifier diode to serve as the first pin of the DC output end of the rectifier circuit;

The anode of the third rectifier diode is electrically connected to the anode of the second rectifier diode to serve as the second pin of the DC output end of the rectifier circuit.

Still further, the voltage regulator circuit includes a voltage regulator tube and a filter capacitor; the negative electrode of the voltage regulator tube is electrically connected to the first pin of the filter capacitor, and the positive electrode of the voltage regulator tube is electrically connected to the filter capacitor. The second pin is electrically connected;

The voltage regulator tube is used to limit the DC output voltage of the rectifier circuit, and the filter capacitor is used to stabilize the DC output voltage of the rectifier circuit.

Still further, the access module includes an access button, and the access button is electrically connected to the NFC sensing module and the control module, respectively;

When the access key is in a pressed state, the NFC sensing module and the control module are turned on to trigger the control module.

Further, the switch module includes a radio frequency switch, and the radio frequency switch includes a power input pin, a ground pin, a control pin, a first switch pin and a second switch pin;

The power input pin of the radio frequency switch is electrically connected to the NFC sensing module, and the ground pin is grounded, so that the NFC sensing module provides a working voltage for the radio frequency switch;

The control pin of the radio frequency switch is electrically connected to the control module, the first switch pin of the radio frequency switch is electrically connected to the NFC sensing module, and the second switch pin of the radio frequency switch is electrically connected to the NFC device electrical connection;

The radio frequency switch is used to turn on the electrical connection between the first switch pin and the second switch pin when the control pin has a high level input, so as to turn on the NFC sensing module and the NFC device.

Still further, the switch module further includes a pull-down resistor, the first pin of the pull-down resistor is electrically connected to the control pin of the radio frequency switch, and the second pin is grounded;

The pull-down resistor is used to disconnect the electrical connection between the first switch pin and the second switch pin when the NFC sensing module just generates a DC output, so as to disconnect the NFC sensing module from the NFC device .

Further, the control module includes a first analog switch, and the first analog switch includes a power input pin, a ground pin, a control pin, a switch pin, and an output pin;

The power input pin of the first analog switch is electrically connected to the NFC sensing module, and the ground pin is grounded, so that the NFC sensing module provides a working voltage for the first analog switch;

The control pin of the first analog switch is electrically connected with the access module, the switch pin is electrically connected with the power input pin, and the output pin is electrically connected with the switch module;

The first analog switch is used to turn on the switch pin and the output pin when the control pin has a high-level input, so that the first analog switch outputs a high-level signal to the switch module.

Still further, the control module further includes a second analog switch, and the second analog switch includes a power input pin, a ground pin, a control pin, a switch pin and an output pin;

The power input pin of the second analog switch is electrically connected to the NFC sensing module, and the ground pin is grounded, so that the NFC sensing module provides a working voltage for the second analog switch;

The control pin of the second analog switch is electrically connected to the access module, the switch pin is electrically connected to the power input pin, and the output pin is electrically connected to the control pin and the control pin of the first analog switch respectively ;

The second analog switch is used to turn on the switch pin and the output pin when the control module is triggered and there is a working voltage input, and send the output pin to the control pin and the first analog switch simultaneously through the output pin. The control pin outputs a high-level signal to maintain the conduction between the switch pin and the output pin of the second analog switch and maintain the conduction between the switch pin and the output pin of the first analog switch. Pass.

Further, the NFC read-write control circuit further includes a power-off delay module, the first pin of the power-off delay module is electrically connected to the access module and the control module, and the second pin is grounded;

The power-off delay module is used to take power from the NFC sensing module and store it when the access module is triggered, and provide the control module with a predetermined time when the NFC sensing module cannot output normal voltage. High level input.

Still further, the power-off delay module includes a delay capacitor and a delay resistor;

The first pin of the delay capacitor is electrically connected to the first pin of the delay resistor to be used as the first pin of the power-off delay module;

The second pin of the delay capacitor is electrically connected to the second pin of the delay resistor to serve as the second pin of the power-off delay module.

In a second aspect, the present invention provides an NFC device, comprising the NFC access control circuit according to the first aspect, when the NFC device is close to an NFC reading and writing device, the NFC device is controlled by the NFC access control circuit Can be accessed by NFC read/write devices.

Beneficial effects: The NFC access control circuit and the NFC device provided by the present invention include NFC equipment, an NFC sensing module, a switch module, an access module and a control module. When the user does not need to use the NFC device, the switch module has no high-level input, so The NFC sensor module and the NFC device are disconnected, and the NFC read-write device cannot access the NFC device. When the user needs to use the NFC device, he only needs to trigger the access module once, and the control module will output a high-level signal to the switch module to turn on the NFC sensing module and the NFC device, so that the NFC device can be accessed. In addition, after the user operation is completed and the NFC device leaves the NFC read-write device, the NFC sensor module and the NFC device are disconnected because the control module will no longer output a high-level signal to the switch module, so the NFC device cannot be accessed. It can be seen that the NFC access control circuit provided by the present invention is not only extremely convenient to operate, but also has no potential safety hazard.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments described in the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

1 is a circuit schematic diagram of an NFC access control circuit provided by a specific embodiment of the present invention;

2 is a schematic circuit diagram of an NFC sensing module in a specific embodiment of the present invention;

3 is a circuit schematic diagram of a conversion circuit in an NFC sensing module in a specific embodiment of the present invention;

4 is a schematic circuit diagram of a switch module in a specific embodiment of the present invention;

5 is a circuit schematic diagram of a control module in a specific embodiment of the present invention;

FIG. 6 is a circuit schematic diagram of a power-off delay module in a specific embodiment of the present invention.

Detailed ways

In order to make those skilled in the art better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only These are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The existing NFC device can be directly accessed by the NFC reading and writing device, so there is a great security risk. In order to solve this technical problem, in the embodiment of the present invention, a switch module is set between the NFC sensing module and the NFC device, and an access module is set to control the on-off of the switch module. In this way, when the user does not need to perform data reading and writing operations, the switch module between the NFC sensing module and the NFC device is disconnected, so even if the NFC reading and writing device is close to the NFC device at this time, the NFC reading and writing device cannot perform access. When the user needs to perform data reading and writing operations, he only needs to trigger the switch module through the access module to turn on the NFC sensing module and the NFC device, so that the data reading and writing operations can be performed.

For example, the embodiments of the present invention may be applied to the following scenarios. In this scenario, when the user carries the electronic cash card for capital transaction operation, the electronic cash card needs to be close to the NFC reading and writing device of the merchant, and the electronic cash card can be accessed by the NFC reading and writing device through the access module, and then the capital transaction operation can be performed. . When the user does not need to use the electronic cash card, even when other people bring the NFC reading and writing device close to the electronic cash card, because the user does not trigger the access module, others cannot perform operations such as deducting the user's balance. Therefore, the electronic cash card to which the embodiments of the present invention are applied does not have the problem of potential safety hazards.

It should be noted that the above application scenarios are only shown for the convenience of understanding the present invention, and the embodiments of the present invention are not limited in this respect. Rather, embodiments of the present invention can be applied to any scenario where applicable.

In order to make the above objects, features and advantages of the present invention more clearly understood, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

Referring to FIG. 1, an NFC access control circuit provided by an embodiment of the present invention is applied to an NFC device, and the circuit includes an NFC device 10, an NFC sensing module 20, a switch module 30, an access module 40, and a control module 50.

The NFC sensing module 20 is electrically connected to the switch module 30, and the switch module 30 is electrically connected to the NFC device 10; the NFC sensing module 20 is also electrically connected to the access module 40, and the access The module 40 is electrically connected to the control module 50 , and the control module 50 is electrically connected to the switch module 30 .

Specifically, when the NFC device is close to the NFC reading and writing device, the NFC sensing module 20 is used to generate an induced current and output a DC voltage. If the NFC sensing module and the NFC device 10 are directly electrically connected Direct access to this NFC device is possible.

Therefore, as an improvement, in this embodiment, a switch module 30 is arranged between the NFC sensing module 20 and the NFC device 10 , and an access module 40 is arranged to control the switch module 30 on and off. Specifically, the access module 40 is used to turn on the NFC sensing module 20 and the control module 50 only when in a triggered state, so as to trigger the control module 50; the control module 50 is used to trigger backward The switch module 30 outputs a high-level signal to trigger the switch module 30; the switch module 30 is used to turn on the NFC sensing module 20 and the NFC device 10 when triggered, so as to enable the NFC The device can be accessed by NFC read and write devices.

Specifically, when the user does not need to use the NFC device, the NFC sensing module 20 and the NFC device 10 are disconnected through the switch module 30, so that others cannot use the NFC reading and writing device to access the NFC device. When the user needs to use the NFC device, he only needs to trigger the access module 40 once, and the access module 40 turns on the NFC sensing module 20 and the control module 50 only in the triggered state to trigger the control module 50; the control module 50 is switched back after being triggered The module 30 outputs a high level to trigger the switch module 30; when the switch module 30 is in a triggered state, the NFC sensing module 20 and the NFC device 10 are turned on, so that the NFC device can be accessed by the NFC read-write device.

Further, referring to FIG. 2 , the above-mentioned NFC sensing module 20 includes an NFC antenna 201 and a conversion circuit 202; the NFC antenna 201 is electrically connected to the AC input end of the conversion circuit 202, and the DC output end of the conversion circuit 202 is respectively Electrically connected with the access module 40, the power input terminal of the control module 50 (not shown in FIG. 2) and the power input terminal of the switch module 30 (not shown in FIG. 2), the NFC antenna 201 is also connected to the switch module 30 is electrically connected;

Wherein, the NFC antenna 201 is used to generate an AC output when the NFC device is close to the NFC reading and writing device; the conversion circuit 202 is used to convert the AC output generated by the NFC antenna 201 into a DC and output a DC voltage.

Specifically, when the NFC device is close to the NFC reading and writing device, the NFC antenna 201 will generate an AC output, but since the switch module 30 is arranged between the NFC antenna 201 and the NFC device 10, the NFC antenna 201 and the NFC device 10 are not conducting.

However, in order to meet the needs of users, it is necessary to control the conduction of the switch module 30 . Compared with the AC signal, the DC signal is more suitable for the control circuit, so the conversion circuit 202 is provided to convert the AC output generated by the NFC antenna 201 into a DC output for controlling the switch module 30 .

In addition, since both the control module 50 and the switch module 30 need the input of the working voltage to work normally, the DC output terminal of the conversion circuit 202 is electrically connected to the power input terminal of the control module 50 and the power input terminal of the switch module 30, respectively. The control module 50 and the switch module 30 provide the operating voltage.

Further, please refer to FIG. 3 , the conversion circuit 202 includes a rectifier circuit 2021 and a voltage regulator circuit 2022 , the NFC antenna 201 is electrically connected to the AC input terminal of the rectifier circuit 2021 , and the DC output terminal of the rectifier circuit 2021 is electrically connected. It is electrically connected to the voltage regulator circuit 2022, and the voltage regulator circuit 2022 is electrically connected to the power input terminal of the access module 40, the control module 50 (not shown in FIG. 3) and the power input terminal of the switch module 30. connection (not shown in Figure 3).

The rectifier circuit 2021 is used for rectifying the AC output generated by the NFC antenna 201 into a DC output; the voltage regulator circuit 2022 is used for limiting and stabilizing the DC output voltage of the rectifier circuit 2021 .

Specifically, the AC output generated by the NFC antenna 201 is not necessarily stable, so the DC output of the rectifier circuit 2021 is also unstable. Therefore, the DC output voltage of the rectifier circuit 2021 is limited and stabilized by the voltage regulator circuit 2022, so as to improve the reliability of the NFC control circuit of this embodiment.

In addition, it should be noted that a pin of the rectifier circuit 2021 and a pin of the voltage regulator circuit 2022 are connected to a common ground.

Still further, please refer to FIG. 3 , the above-mentioned rectifier circuit 2021 includes a first rectifier diode D1 , a second rectifier diode D2 , a third rectifier diode D3 and a fourth rectifier diode D4 .

Specifically, the anode of the first rectifier diode is electrically connected to the negative stage of the third rectifier diode to be used as the first pin of the AC input end of the rectifier circuit 2021; the anode of the second rectifier diode is electrically connected to the negative stage of the fourth rectifier diode. connected to be used as the second pin of the AC input end of the rectifier circuit 2021;

The cathode of the first rectifier diode is electrically connected to the cathode of the second rectifier diode to serve as the first pin of the DC output end of the rectifier circuit 2021; the anode of the third rectifier diode is electrically connected to the anode of the second rectifier diode to Used as the second pin of the DC output terminal of the rectifier circuit 2021 .

In this embodiment, the diodes may be switch diodes or Schottky diodes of the same type or different types.

Still further, please refer to FIG. 3, the above-mentioned voltage regulator circuit 2022 includes a voltage regulator tube DW1 and a filter capacitor C1; the negative electrode of the voltage regulator tube is electrically connected to the first pin of the filter capacitor, and the voltage regulator tube is The positive electrode is electrically connected to the second pin of the filter capacitor.

Specifically, the voltage regulator tube is used to limit the DC output voltage of the rectifier circuit 2021 , and the filter capacitor is used to stabilize the DC output voltage of the rectifier circuit 2022 .

Further, the above-mentioned access module 40 includes an access button, and the access button is electrically connected to the NFC sensing module 20 and the control module 50 respectively; The NFC sensing module 20 and the control module 50 trigger the control module 50 .

Specifically, when the user needs to use the NFC device, if the user needs to keep pressing the button to use it, not only the user experience will be poor, but also the access will fail if the button vibrates during the pressing process; After the user presses the button (or toggles the button), the button remains in the pressed (or toggled) state. Although the user can perform this operation, it is easy for the user to forget to restore the button to the one before pressing after the operation is completed. (or before the toggle), so that the user's NFC device may still be accessed by the NFC read-write device after use.

Based on this, in this embodiment, when the user needs to use the NFC device, he only needs to press the access button once to complete the operation. After this operation is completed, the access button is in a disconnected state, so the NFC read-write device cannot access the NFC device. In this way, not only the user experience is better, but also the security is extremely high.

Further, referring to FIG. 4 , the above-mentioned switch module 30 includes a radio frequency switch 301, and the radio frequency switch 301 includes a power input pin (not shown in FIG. 4 ), a ground pin (GND), a control pin (CTRL), a first A switch pin (S1) and a second switch pin (S2).

Wherein, the power input pin of the radio frequency switch 301 is electrically connected to the NFC sensing module 20 , and the ground pin is grounded, so that the NFC sensing module 20 provides a working voltage for the radio frequency switch 301 .

The control pin of the radio frequency switch 301 is electrically connected to the control module 50 , the first switch pin of the radio frequency switch 301 is electrically connected to the NFC sensing module 20 , the second switch pin of the radio frequency switch 301 is electrically connected It is electrically connected with the NFC device 10 .

The radio frequency switch 301 is used to turn on the electrical connection between the first switch pin and the second switch pin when the control pin has a high level input.

Specifically, when the control pin of the radio frequency switch 301 has a high-level signal input, the two switch pins of the radio frequency switch 301 are turned on. In this way, an electrical connection is formed between the NFC sensing module 20 and the NFC device 10. Makes the NFC device accessible to the NFC read/write device.

In this embodiment, the radio frequency switch 301 selects SKY13453-385LF from SKYWORKS Company. Of course, other switch chips with similar functions can also be selected.

Still further, please refer to FIG. 4 , the switch module 30 further includes a pull-down resistor R1 , the first pin of the pull-down resistor is electrically connected to the control pin of the radio frequency switch 301 , and the second pin is grounded.

The pull-down resistor is used to disconnect the electrical connection between the first switch pin and the second switch pin when the NFC sensing module 20 just generates a DC output, so as to disconnect the NFC sensing module 20 from the Connection of the NFC device 10 .

Specifically, in order to ensure that the switch module 30 can be reliably disconnected from the NFC sensor module 20 and the NFC device 10 when the switch module 30 is just powered on (that is, when the NFC sensor module just generates an output), a pull-down resistor is set in series between its control pin and the ground. In this way, it can be ensured that there is no high-level input on the control pin when the power is just turned on, so it can be ensured that the NFC sensing module 20 and the NFC device 10 are disconnected when the power is just turned on, which improves the reliability of the NFC access control circuit in this embodiment.

Further, please refer to FIG. 5 , the above-mentioned control module 50 includes a first analog switch 501, and the first analog switch 501 includes a power input pin (VCC), a ground pin (GND), a control pin (CTRL), a switch pin (S) and output pin (OUT).

The power input pin of the first analog switch 501 is electrically connected to the NFC sensing module 20 , and the ground pin is grounded, so that the NFC sensing module 20 provides the first analog switch 501 with a working voltage.

The control pin of the first analog switch 501 is electrically connected to the access module 40 , the switch pin is electrically connected to the power input pin, and the output pin is electrically connected to the switch module 30 .

Specifically, the first analog switch 501 is used to turn on the switch pin and the output pin when the control pin has a high level input, so that the first analog switch 501 outputs a high level to the switch module 30 level signal.

Still further, the above-mentioned control module 50 also includes a second analog switch 502, and the second analog switch 502 includes a power input pin (VCC), a ground pin (GND), a control pin (CTRL), a switch pin ( S) and the output pin (OUT).

The power input pin of the second analog switch 502 is electrically connected to the NFC sensing module 20 , and the ground pin is grounded, so that the NFC sensing module 20 provides the second analog switch 502 with a working voltage.

The control pin of the second analog switch 502 is electrically connected with the access module 40, the switch pin is electrically connected with the power input pin, and the output pin is respectively connected with the control pin and the control pin of the first analog switch 501. electrical connection.

Specifically, the second analog switch 502 is used to turn on the switch pin and the output pin after the control module 50 is triggered and there is a working voltage input, and simultaneously send the control pin and the output pin to the control pin and the output pin through the output pin. The control pin of the first analog switch 501 outputs a high level signal to maintain the conduction between the switch pin and the output pin of the second analog switch 502 and to maintain the switch pin of the first analog switch 501 and conduction between the output pins.

In this embodiment, the user only needs to press the access module 40 (access key) to use the NFC device, but the time that the access module 40 is in the triggered state (that is, the access key is in the pressed state) is very short. After successful completion, the first analog switch 501 and the second analog switch 502 are set to simulate the state when the access button is pressed. The specific implementation process is as follows:

(1) When the user presses the access button, the NFC sensing module 20 outputs a high-level signal to the control pins of the two analog switches at the same time, and the switch pins and the output pins of the two analog switches are turned on respectively. , and since the switch pin is connected to the power input pin, the output pins of the two analog switches can output a high-level signal at this time.

(2) Since the access button is in the pressed state for a very short time, the NFC sensing module 20 will not output high-level signals to the control pins of the two analog switches at the same time, so the output pins of the second analog switch 502 are set is electrically connected to its control pin. In this way, even if the control pins of the two analog switches lose the high-level input from the NFC sensing module 20, as long as there is an input of the operating voltage (that is, the NFC sensing module 20 also generates an output), the second analog switch 502 will The output pin will continue to output high-level input to the two control pins at the same time, so as to keep the switch pin and the output pin of the two analog switches connected, so that the output pin of the first analog switch 501 continues to be connected to the output pin of the first analog switch 501. The control pin of the switch module 30 outputs a high level signal. In this way, the NFC device can be accessed by the NFC read-write device.

(3) When the user completes the operation and the NFC sensing module 20 no longer generates output, since the two analog switches have lost their working voltages, the output pins of the two analog switches can no longer output high-level signals, thus breaking the Turn on the NFC sensing module 20 and the NFC device 10.

It is simply understood that the control module 50 is triggered after the access key is pressed, and can continue to output a high-level signal to the switch module 30 as long as the operating voltage is input. Therefore, when users need to operate, they only need to press the access button, which is very convenient.

Further, referring to FIG. 6 , the NFC access control circuit in this embodiment further includes a power-off delay module 60 , the first pin of the power-off delay module 60 is connected to the access module 40 and the control module 50 is electrically connected, and the second pin is grounded; the power-off delay module 60 is used for taking electricity from the NFC sensing module 20 and storing it when the access module 40 is triggered, and when the NFC sensing module 20 cannot When the normal voltage is output, a high level input is provided to the control module 50 for a predetermined time.

Further, please continue to refer to FIG. 6, the power-off delay module 60 includes a delay capacitor C2 and a delay resistor R1; the first pin of the delay capacitor and the first pin of the delay resistor electrically connected to serve as the first pin of the power-off delay module 60; the second pin of the delay capacitor is electrically connected to the second pin of the delay resistor to serve as the power-off delay module 60; The second pin of the electrical delay module 60 .

Specifically, the NFC sensing module 20 will inevitably generate discontinuous DC output due to instability. In this case, it cannot be guaranteed that the control module 50 can always simulate the triggered state of the access module 40, resulting in failure of the access operation. Therefore, in order to improve the reliability of the NFC access control circuit, when the output of the NFC sensing module 20 is unstable, the delay capacitor is discharged through the delay resistor to output a high-level signal for a predetermined time to the control module 50 to ensure that Access operations go smoothly, improving reliability. The specific output time is related to the delay capacitor and delay resistor. For example, assuming that the predetermined time t is 3 seconds, the delay capacitor and the delay resistor can be calculated according to the formula RC=t/ln(V0/Vt), where V0 is the initial voltage value of the delay capacitor and Vt is the time t The voltage value of the delay capacitor, assuming that the minimum high-level signal input of the first or second analog switch 502 is 2.4V, then Vt is set to 2.4V, and assuming that V0 is 5V, then RC=4.09 is calculated according to the formula, If the delay capacitor is selected as 1uF, the delay resistance is about 4.7MΩ.

In addition, since the power-off delay module 60 is set, when the user completes the operation and the NFC sensing module 20 no longer generates output, the power-off delay module 60 will also output a high-level signal for a predetermined time, that is, after the For a predetermined time, the connection between the NFC sensing module 20 and the NFC device 10 is still conducted.

To sum up, the NFC access control circuit provided in this embodiment includes an NFC device 10 , an NFC sensing module 20 , a switch module 30 , an access module 40 and a control module 50 . When the user does not need to use the NFC device, since the switch module 30 has no high-level input, the NFC sensing module 20 and the NFC device 10 are disconnected, and the NFC reading and writing device cannot access the NFC device. When the user needs to use the NFC device, he only needs to trigger the access module 40, and the control module 50 will output a high-level signal to the switch module 30 to turn on the NFC sensing module 20 and the NFC device 10, so that the NFC device can be accessed. In addition, after the user operation is completed and the NFC device leaves the NFC reading and writing device, since the control module 50 will no longer output a high-level signal to the switch module 30, the NFC sensing module 20 and the NFC device 10 are disconnected, so the NFC device 10 cannot be accessed. It can be seen that the NFC access control circuit provided in this embodiment is not only extremely convenient to operate, but also has no potential safety hazard.

Based on the same inventive concept, another embodiment of the present invention provides an NFC device, including the NFC access control circuit described above, when the NFC device is close to the NFC reading and writing device, the NFC access control circuit controls the The NFC device can be accessed by the NFC read-write device.

Since the present embodiment and the above-mentioned embodiments are based on the same inventive concept, reference may be made to the above-mentioned embodiments for the specific implementation thereof, and repeated descriptions will not be repeated.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention. should be included within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (10)

1. An NFC access control circuit, applied to an NFC device, wherein the NFC access control circuit comprises an NFC device, an NFC induction module, a switch module, an access module and a control module; The NFC sensing module is electrically connected with the switch module, and the switch module is electrically connected with the NFC device; the NFC sensing module is also electrically connected with the access module, and the access module is electrically connected with the control module , the control module is electrically connected with the switch module; The NFC sensing module is used to generate an induced current and output a DC voltage when the NFC device is close to the NFC reading and writing device; The access module is configured to turn on the NFC sensing module and the control module only when in a triggered state to trigger the control module; The control module is configured to output a high-level signal to the switch module after being triggered to trigger the switch module; The switch module is used to turn on the NFC sensing module and the NFC device when triggered, so that the NFC device can be accessed by the NFC reading and writing device; The access module includes an access key, and the access key is electrically connected to the NFC sensing module and the control module, respectively; When the access button is in a pressed state, turn on the NFC sensing module and the control module to trigger the control module; The switch module includes a radio frequency switch, and the radio frequency switch includes a power input pin, a ground pin, a control pin, a first switch pin and a second switch pin; The power input pin of the radio frequency switch is electrically connected to the NFC sensing module, and the ground pin is grounded, so that the NFC sensing module provides a working voltage for the radio frequency switch; The control pin of the radio frequency switch is electrically connected to the control module, the first switch pin of the radio frequency switch is electrically connected to the NFC sensing module, and the second switch pin of the radio frequency switch is electrically connected to the NFC device electrical connection; The radio frequency switch is used to turn on the electrical connection between the first switch pin and the second switch pin when the control pin has a high level input, so as to turn on the NFC sensing module and the NFC device. 2 . The NFC access control circuit according to claim 1 , wherein the NFC sensing module comprises an NFC antenna and a conversion circuit, the NFC antenna is electrically connected to an AC input end of the conversion circuit, and the conversion circuit is electrically connected. 3 . The DC output terminals are respectively electrically connected to the access module, the power input terminal of the control module and the power input terminal of the switch module, and the NFC antenna is also electrically connected to the switch module; The NFC antenna is used to generate an AC output when the NFC device is close to the NFC read-write device; the conversion circuit is used to convert the AC output generated by the NFC antenna into a DC and output a DC voltage. 3. The NFC access control circuit according to claim 2, wherein the conversion circuit comprises a rectifier circuit and a voltage regulator circuit, the NFC antenna is electrically connected to an AC input end of the rectifier circuit, and the rectifier circuit The DC output terminal of the device is electrically connected to the voltage regulator circuit, and the voltage regulator circuit is electrically connected to the access module, the power input terminal of the control module and the power input terminal of the switch module; The rectifier circuit is used to rectify the AC output generated by the NFC antenna into a DC output; the voltage regulator circuit is used to limit and stabilize the DC output voltage of the rectifier circuit; The rectifier circuit includes a first rectifier diode, a second rectifier diode, a third rectifier diode and a fourth rectifier diode; The anode of the first rectifier diode is electrically connected to the negative stage of the third rectifier diode to serve as the first pin of the AC input end of the rectifier circuit; The anode of the second rectifier diode is electrically connected to the negative stage of the fourth rectifier diode to serve as the second pin of the AC input end of the rectifier circuit; The cathode of the first rectifier diode is electrically connected to the cathode of the second rectifier diode to serve as the first pin of the DC output end of the rectifier circuit; The anode of the third rectifier diode is electrically connected to the anode of the second rectifier diode to serve as the second pin of the DC output end of the rectifier circuit. 4. The NFC access control circuit according to claim 3, wherein the voltage regulator circuit comprises a voltage regulator tube and a filter capacitor; the negative electrode of the voltage regulator tube is electrically connected to the first pin of the filter capacitor , the positive pole of the voltage regulator tube is electrically connected to the second pin of the filter capacitor; The voltage regulator tube is used to limit the DC output voltage of the rectifier circuit, and the filter capacitor is used to stabilize the DC output voltage of the rectifier circuit. 5. The NFC access control circuit according to claim 1, wherein the switch module further comprises a pull-down resistor, a first pin of the pull-down resistor is electrically connected to a control pin of the radio frequency switch, and a second pin of the pull-down resistor is electrically connected to the control pin of the radio frequency switch. pin to ground; The pull-down resistor is used to disconnect the electrical connection between the first switch pin and the second switch pin when the NFC sensing module just generates a DC output, so as to disconnect the NFC sensing module from the NFC device . 6. The NFC access control circuit according to claim 1, wherein the control module comprises a first analog switch, and the first analog switch comprises a power input pin, a ground pin, a control pin, a switch lead pins and output pins; The power input pin of the first analog switch is electrically connected to the NFC sensing module, and the ground pin is grounded, so that the NFC sensing module provides a working voltage for the first analog switch; The control pin of the first analog switch is electrically connected with the access module, the switch pin is electrically connected with the power input pin, and the output pin is electrically connected with the switch module; The first analog switch is used to turn on the switch pin and the output pin when the control pin has a high-level input, so that the first analog switch outputs a high-level signal to the switch module. 7. The NFC access control circuit according to claim 6, wherein the control module further comprises a second analog switch, and the second analog switch comprises a power input pin, a ground pin, a control pin, a switch pins and output pins; The power input pin of the second analog switch is electrically connected to the NFC sensing module, and the ground pin is grounded, so that the NFC sensing module provides a working voltage for the second analog switch; The control pin of the second analog switch is electrically connected to the access module, the switch pin is electrically connected to the power input pin, and the output pin is electrically connected to the control pin and the control pin of the first analog switch respectively ; The second analog switch is used to turn on the switch pin and the output pin when the control module is triggered and there is a working voltage input, and send the output pin to the control pin and the first analog switch simultaneously through the output pin. The control pin outputs a high-level signal to maintain the conduction between the switch pin and the output pin of the second analog switch and maintain the conduction between the switch pin and the output pin of the first analog switch. Pass. 8. The NFC access control circuit according to claim 1, wherein the NFC access control circuit further comprises a power-off delay module, the first pin of the power-off delay module is connected to the access module and the The control module is electrically connected, and the second pin is grounded; The power-off delay module is configured to take power from the NFC sensing module and store it when the access module is triggered, and provide the control module with power for a predetermined time when the NFC sensing module cannot output normal voltage. High level input. 9. The NFC access control circuit according to claim 8, wherein the power-off delay module comprises a delay capacitor and a delay resistor; The first pin of the delay capacitor is electrically connected to the first pin of the delay resistor to be used as the first pin of the power-off delay module; The second pin of the delay capacitor is electrically connected to the second pin of the delay resistor to serve as the second pin of the power-off delay module. 10. An NFC device, characterized in that it comprises the NFC access control circuit according to any one of claims 1-9, and when the NFC device is close to an NFC read-write device, the NFC access control circuit controls all the devices. The NFC device can be accessed by the NFC read-write device.

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