CN115085770B

CN115085770B - Passive NFC interface and device

Info

Publication number: CN115085770B
Application number: CN202110276363.8A
Authority: CN
Inventors: 卢友顺; 赵晶剑
Original assignee: Shanghai Fudan Microelectronics Group Co Ltd
Current assignee: Shanghai Fudan Microelectronics Group Co Ltd
Priority date: 2021-03-15
Filing date: 2021-03-15
Publication date: 2023-07-28
Anticipated expiration: 2041-03-15
Also published as: CN115085770A

Abstract

The embodiment of the invention provides a passive NFC interface and equipment. The passive NFC interface includes: the sensing module is used for sensing a radio frequency signal sent by the active NFC equipment and generating a first radio frequency voltage based on the radio frequency signal; the control module is connected with the induction module and used for receiving and communicating with the active NFC equipment based on radio frequency signals; the energy storage module is connected with the induction module and used for receiving and storing electric energy generated based on the first radio frequency voltage; the input end of the voltage reducing module is connected with the induction module, the output end of the voltage reducing module is connected with the control module and is used for receiving and reducing the first radio frequency voltage to form a second radio frequency voltage and outputting the second radio frequency voltage to the control module. Therefore, the pressure difference between the energy storage module and the control module and the electric energy stored by the energy storage module can be improved, so that the loss of radio frequency energy is avoided, and the energy conversion efficiency of the passive NFC interface is improved.

Description

Passive NFC interface and device

Technical Field

The present invention relates to the field of wireless communications technologies, and in particular, to a passive NFC interface and a device.

Background

Since near field communication (Near Field Communication, NFC) uses a magnetic field as an information carrier, a communication distance (several centimeters) much shorter than that of conventional wireless communication is achieved, and the near field communication has the advantages of passive communication, high security, wide use and the like. Therefore, applications based on NFC technology are also becoming more widespread, such as new fingerprint cards, new visual cards, smart wearable devices, passive NFC smart locks, passive electronic ink tags, etc.

Typically, a passive NFC interface is capable of receiving radio frequency energy from an active NFC interface to power itself and external loads. However, the design of the existing passive NFC interface is derived from RFID technology, so that the energy receiving efficiency is low, and only simple operations, such as reading and writing internal memory, can be maintained, which greatly limits the performance and application of the NFC interface.

Disclosure of Invention

The technical problem solved by the embodiment of the invention is how to improve the energy conversion efficiency of the passive NFC interface.

In order to solve the technical problems, the embodiment of the invention provides a passive NFC interface and equipment.

The passive NFC interface provided by the embodiment of the invention comprises the following components: the sensing module is used for sensing a radio frequency signal sent by the active NFC equipment and generating a first radio frequency voltage based on the radio frequency signal; the control module is connected with the induction module and used for receiving and communicating with the active NFC equipment based on radio frequency signals; the energy storage module is connected with the induction module and used for receiving and storing electric energy generated based on the first radio frequency voltage; the input end of the voltage reducing module is connected with the induction module, the output end of the voltage reducing module is connected with the control module and is used for receiving and reducing the first radio frequency voltage to form a second radio frequency voltage and outputting the second radio frequency voltage to the control module. In this way, the pressure difference between the energy storage module and the control module can be increased.

Optionally, the second radio frequency voltage is located within an operating voltage range of the control module.

Optionally, the step-down module is connected in series with the control module and then connected in parallel with the induction module.

Optionally, the buck module includes at least one set of buck elements connected between the sense module and the control module.

Optionally, the control module receives the radio frequency signal through a differential radio frequency signal line, the differential radio frequency signal line includes a first radio frequency signal line and a second radio frequency signal line, and the at least one set of voltage reducing elements includes a first set of voltage reducing elements and a second set of voltage reducing elements connected in series between the sensing module and the control module through the first radio frequency signal line and the second radio frequency signal line, respectively.

Optionally, each of the at least one set of voltage reduction elements comprises at least one first voltage reduction element having a fixed voltage drop.

Optionally, each of the at least one set of voltage reducing elements comprises at least two first voltage reducing elements connected in series with each other.

Optionally, the first voltage reducing element comprises a diode.

Optionally, the diode comprises a light emitting diode.

Optionally, each of the at least one set of voltage reduction elements includes a second voltage reduction element having a non-fixed voltage drop.

Optionally, the second voltage reducing element comprises a capacitor.

Optionally, the energy storage module comprises a rectifying unit connected with the induction module in parallel and an energy storage unit connected with the rectifying unit, wherein the input end of the rectifying unit is connected with the induction module, and the output end of the rectifying unit is connected with the energy storage unit.

Optionally, the energy storage module includes a clipping unit connected between the rectifying unit and the energy storage unit, for clipping the output voltage of the rectifying unit.

Optionally, the energy storage module includes a charging control unit connected between the rectifying unit and the energy storage unit, and is configured to control the energy storage unit to perform low-current charging when the charging parameter of the energy storage unit is less than the parameter threshold value, and to control the energy storage unit to perform high-current charging when the charging parameter is greater than or equal to the parameter threshold value.

Optionally, the charging system comprises an acquisition module which is respectively connected with the control module and the energy storage unit and is used for acquiring the charging parameters.

Optionally, the charging parameters include a charging time, a charging voltage, and/or a charging amount.

The passive NFC device provided by the embodiment of the invention comprises the passive NFC interface.

Optionally, the passive NFC device includes a passive electronic screen, a passive electronic lock, and a passive wearable device.

Compared with the prior art, the technical scheme of the embodiment of the invention has the beneficial effects.

For example, the voltage-reducing module is used for reducing the first radio frequency voltage output by the sensing module to the second radio frequency voltage and outputting the second radio frequency voltage to the control module, so that the pressure difference between the energy storage module and the control module and the electric energy stored by the energy storage module can be improved, the loss of radio frequency energy is avoided, the energy conversion efficiency of the passive NFC interface is improved, and the performance improvement and the application range expansion of the passive NFC interface are facilitated.

For another example, by reducing the second radio frequency voltage to the working voltage interval of the control module, the first radio frequency voltage output by the induction module can be prevented from being limited by the limiting circuit in the control module, so that the pressure difference between the energy storage module and the control module is further improved, and the energy conversion efficiency of the passive NFC interface is further improved.

For another example, since the voltage reduction module is adopted to effectively improve the voltage difference between the energy storage module and the control module so as to improve the electric energy stored by the energy storage module, the passive NFC interface can have good energy collection effect even if an NFC antenna is adopted, and the design difficulty of the antenna can be simplified and the occupied space of the antenna can be reduced so as to reduce the volume of the equipment, thereby saving the cost.

For another example, the diode is used as the voltage reducing element, so that the circuit design is simple, the cost is low, and the resonant frequency of the sensing module is not affected due to the fact that the parallel equivalent capacitance of the diode is small (if the parallel equivalent capacitance of the voltage reducing element is large, the parallel equivalent capacitance changes along with the change of the electromagnetic field intensity, and therefore the resonant frequency of the sensing module is affected).

For another example, the voltage drop of the light emitting diode is larger, so that the voltage difference between the energy storage module and the control module can be effectively improved, and the energy conversion efficiency of the passive NFC interface can be effectively improved by only adopting one light emitting diode in each group of voltage reduction elements.

For another example, the appropriate distance and the relative position between the passive NFC interface and the active NFC device can be quickly found by the brightness of the light emitting diode, so that the passive NFC interface can receive the strongest radio frequency energy from the active NFC device, and energy conversion efficiency is improved.

For another example, when the passive NFC interface supplies power to the load based on the electric energy stored by the energy storage unit to drive the load to move (for example, when the passive electronic lock is unlocked), the brightness of the light emitting diode can be used to quickly determine when to drive the load to move (for example, when the light emitting diode is brightest, the passive electronic lock is triggered to unlock), which is beneficial to improving the working efficiency of the passive NFC interface and the load.

For another example, the capacitor is used as the voltage reducing element, so that not only the circuit design can be simplified, but also the influence on the resonance frequency of the induction module is small due to the small capacitance value of the capacitor.

Drawings

Fig. 1 is a schematic block diagram of a passive NFC interface in an embodiment of the invention;

fig. 2 is a second functional block diagram of a passive NFC interface in an embodiment of the invention;

fig. 3 is a third functional block diagram of a passive NFC interface in an embodiment of the invention.

Detailed Description

In the prior art, the design of the passive NFC interface is derived from the RFID technology, so that the energy receiving efficiency is low, and only simple operations, such as reading and writing an internal memory, can be maintained, so that the performance and the application of the NFC interface are greatly limited.

Unlike the prior art, embodiments of the present invention provide an improved passive NFC interface, comprising: the sensing module is used for sensing a radio frequency signal sent by the active NFC equipment and generating a first radio frequency voltage based on the radio frequency signal; the control module is connected with the induction module and used for receiving and communicating with the active NFC equipment based on radio frequency signals; the energy storage module is connected with the induction module and used for receiving and storing electric energy generated based on the first radio frequency voltage; the input end of the voltage reducing module is connected with the induction module, the output end of the voltage reducing module is connected with the control module and is used for receiving and reducing the first radio frequency voltage to form a second radio frequency voltage and outputting the second radio frequency voltage to the control module.

Compared with the prior art, the passive NFC interface provided by the embodiment of the invention reduces the first radio frequency voltage output by the sensing module into the second radio frequency voltage to be output to the control module by adopting the voltage reduction module, so that the pressure difference between the energy storage module and the control module and the electric energy stored by the energy storage module can be improved, the loss of radio frequency energy is avoided, the energy conversion efficiency of the passive NFC interface is improved, and the improvement of the performance of the passive NFC interface and the expansion of the application range are facilitated.

In order to make the objects, features and advantages of the embodiments of the present invention more comprehensible, the following detailed description of the embodiments of the present invention refers to the accompanying drawings. It is to be understood that the following specific examples are intended to illustrate the invention, and are not to be construed as limiting the invention. Further, it should be noted that, for convenience of description, only some, but not all of the structures related to the present invention are shown in the drawings.

In the various drawings of the embodiments of the invention, like modules or parts are given like reference numerals.

Referring to fig. 1, a passive NFC interface 101 provided in an embodiment of the present invention includes an induction module 110, a step-down module 120, a control module 130, and an energy storage module 140.

Specifically, the sensing module 110 is configured to sense a radio frequency signal emitted by the active NFC device and generate a first radio frequency voltage based on the radio frequency signal; the buck module 120 has an input end connected to the sensing module 110 and an output end connected to the control module 130, and is configured to receive and reduce the first rf voltage to form a second rf voltage for outputting to the control module 130; the control module 130 is configured to receive and communicate with the active NFC device based on the radio frequency signal; the energy storage module 140 is connected to the sensing module 110 for receiving and storing the electric energy generated based on the first rf voltage.

In the embodiment of the present invention, the voltage difference between the energy storage module 140 and the control module 130 can be increased by reducing the first rf voltage output by the sensing module 110 to the second rf voltage by the voltage reduction module 120 and outputting the second rf voltage to the control module 130, so that the electric energy stored by the energy storage module 140 is increased, and the energy conversion efficiency of the passive NFC interface 101 is further improved.

In particular implementations, control module 130 may be implemented using any NFC controller known in the art and having NFC communication functionality.

Typically, NFC controllers are provided with clipping circuits. When the radio frequency voltage output by the sensing module 110 to the NFC controller is greater than the maximum working voltage of the NFC controller, the clipping circuit in the NFC controller will bleed the redundant current and clip the radio frequency voltage generated by the sensing module 110, so as to ensure that the NFC controller can work within the working voltage interval thereof. When the excessive current is discharged and the rf voltage generated by the sensing module 110 is limited, the rf voltage received by the energy storage module 140 and the stored electric energy based on the rf voltage are reduced, thereby reducing the conversion efficiency of the NFC energy.

In the embodiment of the present invention, the passive NFC interface 101 is provided with a step-down module 120, which is configured to receive the first rf voltage output by the sensing module 110 and reduce the first rf voltage to a second rf voltage for outputting to the control module 130. In this way, the clipping degree of the clipping circuit in the NFC controller to the first radio frequency voltage output by the sensing module 110 can be reduced to reduce the loss of NFC energy, so as to improve the energy conversion efficiency of the passive NFC interface 101 and the electrical energy stored in the energy storage module 140.

In some embodiments, the step-down module 120 may reduce the first rf voltage output by the sensing module 110 to be within the operating voltage range of the control module 130, i.e. make the second rf voltage be within the operating voltage range of the control module 130.

In this way, the clipping circuit in the NFC controller may be avoided from clipping the first radio frequency voltage output by the sensing module 110, so as to effectively reduce the loss of NFC energy, thereby improving the electric energy stored by the energy storage module 140 and the energy conversion efficiency of the passive NFC interface 101.

Referring to fig. 2, in an implementation, the sensing module 110 may include an NFC antenna 111 and an antenna matching unit 112 connected to the NFC antenna 111.

Specifically, the NFC antenna 111 and the antenna matching unit 112 may together form a parallel resonant circuit for adjusting the resonant frequency of the NFC antenna 111 to the operating frequency of 13.56Hz, so as to optimize the communication effect and the energy receiving efficiency of the NFC antenna 111.

In a specific implementation, the passive NFC interface 101 may be provided with only one NFC antenna 111.

In implementation, the antenna matching unit 112 may be implemented by any conventional means known in the art, for example, a matching capacitor connected in parallel to the NFC antenna 111.

In a specific implementation, the energy storage module 140 may include a rectifying unit 141 connected in parallel with the sensing module 110 and an energy storage unit 142 connected with the rectifying unit 141.

Specifically, the rectifying unit 141 has an input end connected to the sensing module 110, an output end connected to the energy storage unit 122, and is configured to receive the first rf voltage from the sensing module 110, rectify the first rf voltage, and output the rectified first rf voltage to the energy storage unit 142.

In a specific implementation, the antenna matching unit 112 is connected in parallel with the NFC antenna 111, and the rectifying unit 141 is also connected in parallel with the NFC antenna 111, that is, the rectifying voltage 141, the antenna matching unit 112, and the NFC antenna 111 are connected in parallel.

In implementation, the rectifying unit 141 may be implemented by any conventional technical means known in the art, for example, a bridge rectifying circuit or a synchronous rectifying circuit may be implemented.

In a specific implementation, the voltage reducing module 120 may be connected in series with the control module 130 and then connected in parallel with the sensing module 110, that is, the voltage reducing module 120 and the control module 130 are connected in series and then connected in parallel with the sensing module 110.

In implementations, the buck module 120 may include at least one set of buck elements connected between the sense module 110 and the control module 130.

In some embodiments, the control module 130 receives the rf signal using a differential rf signal line, i.e., the sensing module 110 and the control module 130 are connected by a differential rf signal line.

Specifically, the differential rf signal line includes two rf signal lines, namely a first rf signal line 131 and a second rf signal line 132. The first rf signal line 131 and the second rf signal line 132 are respectively connected between the sensing module 110 and the control module 130, referring to fig. 2.

In this case, the at least one set of voltage step-down elements includes a first set of voltage step-down elements 121 and a second set of voltage step-down elements 122 connected between the sensing module 110 and the control module 130 through a first radio frequency signal line 131 and a second radio frequency signal line 132, respectively, see fig. 2.

In other embodiments, the control module 130 may also receive the rf signal using a single rf signal line that is not differential, i.e., only one rf signal line is used to connect the sensing module 110 and the control module 130.

In this case, the at least one set of voltage reducing elements may include only one set of voltage reducing elements connected between the sensing module 110 and the control module 130 through a single radio frequency signal line.

In some embodiments, each of the at least one set of voltage reduction elements has a fixed voltage drop. In an implementation, the first RF voltage is reduced based on a fixed voltage drop of each set of voltage reduction elements to form the second RF voltage.

In implementations, the fixed voltage drop of each of the at least one set of voltage reduction elements may be determined based on the first radio frequency voltage, the radio frequency voltage desired by the energy storage module 140 (which may be derived based on the electrical energy desired by the energy storage module 140), and the operating voltage interval of the control module 130.

For example, to maximize the voltage differential between the energy storage module 140 and the control module 130, to enable the energy storage module 140 to obtain the most electrical energy based on the sensing module 110, the second rf voltage may be located within the operating voltage range of the control module 130. Knowing that the first rf voltage is 11V and the operating voltage of the control module 130 is 4V,5V, the fixed voltage drop of each of the at least one set of voltage step-down elements is 6V,7V, where 6v=11v-5V and 7v=1v-4V. In this manner, the second RF voltage may be placed within [4V,5V ] to maximize the voltage differential between the energy storage module 140 and the control module 130.

The fixed voltage drops of the first set of voltage dropping elements 121 and the second set of voltage dropping elements 122 are both at [6v,7v ] for the case of the aforementioned connection using differential radio frequency signal lines, and at [6v,7v ] for the case of the aforementioned connection using a single radio frequency signal line and only one set of voltage dropping elements.

In a specific implementation, each of the at least one set of voltage reduction elements may include at least one first voltage reduction element having a fixed voltage drop.

In some embodiments, each of the at least one set of voltage reduction elements may include only one first voltage reduction element, and the fixed voltage drop of each set of voltage reduction elements is equal to the fixed voltage drop of the corresponding first voltage reduction element.

In other embodiments, each of the at least one set of voltage reduction elements may include at least two first voltage reduction elements and the at least two first voltage reduction elements are connected in series, the fixed voltage drop of each set of voltage reduction elements being equal to the sum of the fixed voltage drops of the corresponding at least two first voltage reduction elements connected in series.

In particular, the first voltage step-down element may comprise a diode, in particular a light emitting diode.

Generally, light emitting diodes have a larger voltage drop than other types of diodes. For example, the voltage drop of a red light emitting diode is about 2 volts, and the voltage drops of a white light emitting diode and a blue light emitting diode are about 2.7 volts.

When the light emitting diode with larger voltage drop is used as the first voltage reducing element, each group of voltage reducing elements can only comprise one first voltage reducing element, so that a better voltage reducing effect can be achieved. When diodes with smaller voltage drops are used as the first voltage reducing elements, each group of voltage reducing elements may require at least two first voltage reducing elements in series to achieve a better voltage reducing effect.

In general, the radio frequency energy received by the passive NFC interface 102 has a relationship with the distance and relative position between the passive NFC interface 102 and the active NFC device, and when the distance and relative position between the two are appropriate, the radio frequency energy received by the passive NFC interface 102 from the active NFC device is strongest.

Because the light emitting diode has a light emitting characteristic, a suitable distance and a relative position between the passive NFC interface 102 and the active NFC device can be determined by the brightness of the light emitted by the light emitting diode, so that the radio frequency energy received by the passive NFC interface 102 from the active NFC device is strongest, and the energy conversion efficiency is improved.

In other embodiments, each of the at least one set of voltage reduction elements includes a second voltage reduction element having a non-fixed voltage drop.

Specifically, the second voltage reducing element may include a capacitor.

In some embodiments, each of the at least one set of voltage reduction elements may include only one capacitor.

In a specific implementation, the load characteristic of the control module 130 may be equivalent to a resistor and a capacitor connected in parallel, and the capacitance value of the capacitor may be calculated based on the first rf voltage, the rf voltage expected to be obtained by the energy storage module 140 (obtained based on the electric energy expected to be obtained by the energy storage module 140), and the impedance of the parallel resistor and capacitor, and the specific calculation process is common knowledge in the art and will not be repeated herein.

In a specific implementation, the capacitance values of the capacitors suitable as the second voltage reducing element are small, typically less than 300 picofarads.

In the case of the aforementioned connection using differential rf signal lines, one capacitor of the first group of voltage-reducing elements is connected between the sensing module 110 and the control module 130 through the first rf signal line 131, one capacitor of the second group of voltage-reducing elements is connected between the sensing module 110 and the control module 130 through the second rf signal line 132, and the capacitance value of one capacitor of the first group of voltage-reducing elements is equal to the capacitance value of one capacitor of the second group of voltage-reducing elements.

In the case of the aforementioned connection using a single rf signal line and only one set of voltage reducing elements, one capacitor of the set of voltage reducing elements is connected between the sensing module 110 and the control module 130 via the single rf signal line.

In an embodiment of the present invention, the electric energy stored in the energy storage unit 142 may be used to supply power to the passive NFC interface 102 and the external load.

Referring to fig. 3, the energy storage module 140 may further include a clipping unit 143 connected between the rectifying unit 141 and the energy storage unit 142 to clip the output voltage of the rectifying unit 142, thereby ensuring that the power supply voltage of the energy storage unit 142 to the passive NFC interface 103 and/or the external load does not exceed the operation voltage of the passive NFC interface 103 and/or the external load, so as to ensure that the passive NFC interface 103 and/or the external load can operate normally.

Referring to fig. 3, the energy storage module 140 may further include a charging control unit 144 connected between the rectifying unit 141 and the energy storage unit 142 to control the energy storage unit 142 to perform low-current charging when the charging parameter of the energy storage unit 142 is less than the parameter threshold value, and to control the energy storage unit 142 to perform high-current charging when the charging parameter is greater than or equal to the parameter threshold value.

In general, the passive NFC interface 103 may cause problems such as power failure, communication failure, etc. of the passive NFC interface 103 due to excessive current load at the moment when the passive NFC interface 103 just starts to enter the electromagnetic field emitted by the active NFC device. In this case, the energy storage unit 142 needs to be charged with a small current to ensure that the passive NFC interface 103 is powered up normally and the communication is stable. When the passive NFC interface 103 is powered on normally and the communication is stable, the energy storage unit 142 can be charged with a large current, so as to improve the charging efficiency.

In an embodiment of the present invention, the charging control unit 144 may be used to control the energy storage unit 142 to perform low-current or high-current charging.

Specifically, the charge control unit 144 may be implemented using any conventional technical means known in the art. For example, the charging control unit 144 may be provided with a current limiting resistor, and the charging current of the energy storage unit 142 is limited by the current limiting resistor to perform low-current charging when the passive NFC interface 103 enters the field or the communication is unstable, and the limitation of the charging current by the current limiting resistor is canceled to perform high-current charging after the communication of the passive NFC interface 103 is stable.

In an implementation, the charge control unit 144 may be connected between the clipping unit 143 and the energy storage unit.

Further, the passive NFC interface 103 may further include an acquisition module 150 connected to the energy storage unit 142 for acquiring the charging parameters.

In a specific implementation, whether the passive NFC interface 103 is at the moment of entry or whether the communication is stable may be determined based on the change of the charging parameters such as the charging time, the charging voltage, and the charging power of the energy storage unit 142, so as to enable the energy storage unit 142 to perform the low-current charging at the moment of entry and when the communication is unstable, and enable the energy storage unit 142 to perform the high-current charging when the communication is stable.

In addition, when to perform high-current charging may be selected based on the need of an external load after the passive NFC interface 103 has stabilized communication. For example, when the power demand of the external load is large or power needs to be supplied as soon as possible, the energy storage unit 142 may be charged with a large current as soon as possible after the passive NFC interface 103 is stable in communication. In a specific implementation, it is also possible to determine when to perform the high-current charging through the change of the charging parameters, such as the charging time, the charging voltage, and the charging amount of the energy storage unit 142.

In a specific implementation, corresponding time threshold, voltage threshold, and parameter threshold such as power threshold may be set for charging parameters such as charging time, charging voltage, and charging power, so that the charging control unit 144 may:

controlling the energy storage unit 142 to perform low-current charging when the charging time is less than the time threshold, and controlling the energy storage unit 142 to perform high-current charging when the charging time is greater than or equal to the time threshold, and/or

Controlling the energy storage unit 142 to perform low current charging when the charging voltage is less than the voltage threshold, and controlling the energy storage unit 142 to perform high current charging when the charging voltage is greater than or equal to the voltage threshold, and/or

The energy storage unit 142 is controlled to perform low-current charging when the charge amount is less than the charge amount threshold, and the energy storage unit 142 is controlled to perform high-current charging when the charge amount is greater than or equal to the charge amount threshold.

In an implementation, the control module 130 may be further connected to the charging control unit 144 and the acquisition module 150, respectively, to receive the charging parameter and compare it with a corresponding parameter threshold, and control the charging control unit 144 to perform the low-current charging or the high-current charging on the energy storage unit 142 based on the comparison result.

In implementations, the control module 130 may also be configured to preset the corresponding parameter thresholds.

In some embodiments, parameter thresholds such as a time threshold, a voltage threshold, and a power threshold may be determined based on whether the passive NFC interface 103 communications are stable. For example, the respective parameter threshold may be determined based on the passive NFC interface 103 communication charging time, charging voltage, and charging power just stable or after a period of time.

The time threshold is described below as an example.

When the charging control unit 144 uses the current limiting resistor to limit the charging of the energy storage unit 142, the time threshold may be determined based on the resistance R of the current limiting resistor and the capacitance C of the energy storage unit 142. In general, when the charging time of the energy storage unit 142 reaches a double time constant RC, the communication connection between the passive NFC interface 103 and the active NFC device is already in a stable state, whereby the time threshold can be set to RC.

After determining the time threshold, a transition to a corresponding voltage threshold or charge threshold may be based on the time threshold.

In other embodiments, the time threshold, voltage threshold, and power threshold parameter thresholds may also be determined based on the needs of the external load. For example, when the power demand of the external load is large or power supply is required as soon as possible, the time threshold may be set to one time constant RC, and when the power demand of the external load is small or power supply is not required as soon as possible, the time threshold may be set to 1.5 times the time threshold.

The embodiment of the invention also provides a passive NFC device, which comprises the passive NFC interfaces 101, 102 or 103 provided by the embodiment of the invention.

In particular, passive NFC devices may include passive electronic screens, passive electronic locks, and passive wearable devices.

Although specific embodiments have been described above, these embodiments are not intended to limit the scope of the disclosure, even where only a single embodiment is described with respect to a particular feature. The characteristic examples provided in the present disclosure are intended to be illustrative, not limiting, unless stated differently. In practice, the features of one or more of the dependent claims may be combined with the features of the independent claims where technically possible, according to the actual needs, and the features from the respective independent claims may be combined in any appropriate way, not merely by the specific combinations enumerated in the claims.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention should be assessed accordingly to that of the appended claims.

Claims

1. A passive NFC interface, comprising:

the sensing module is used for sensing a radio frequency signal sent by the active NFC equipment and generating a first radio frequency voltage based on the radio frequency signal;

the control module is connected with the induction module and used for receiving and communicating with the active NFC equipment based on the radio frequency signal;

the energy storage module is connected with the induction module and used for receiving and storing electric energy generated based on the first radio frequency voltage;

and the input end of the voltage reducing module is connected with the induction module, the output end of the voltage reducing module is connected with the control module, and the voltage reducing module is used for receiving and reducing the first radio frequency voltage to form a second radio frequency voltage and outputting the second radio frequency voltage to the control module.

2. The passive NFC interface of claim 1 wherein the second radio frequency voltage is within an operating voltage interval of the control module.

3. A passive NFC interface according to claim 1 or claim 2 wherein the buck module is connected in series with the control module and then in parallel with the sense module.

4. A passive NFC interface according to claim 3 wherein the buck module includes at least one set of buck elements connected between the sense module and the control module.

5. The passive NFC interface of claim 4 wherein the control module receives the radio frequency signals through a differential radio frequency signal line including a first radio frequency signal line and a second radio frequency signal line, the at least one set of buck elements including a first set of buck elements and a second set of buck elements connected in series between the sense module and the control module through the first radio frequency signal line and the second radio frequency signal line, respectively.

6. The passive NFC interface of claim 4 or 5 wherein each of the at least one set of buck elements includes at least one first buck element having a fixed voltage drop.

7. The passive NFC interface of claim 6 wherein each of the at least one set of buck elements includes at least two of the first buck elements in series with each other.

8. The passive NFC interface of claim 6, wherein the first voltage reduction element comprises a diode.

9. The passive NFC interface of claim 8, wherein the diode comprises a light emitting diode.

10. The passive NFC interface of claim 4 or 5 wherein each of the at least one set of buck elements includes a second buck element having a non-fixed voltage drop.

11. The passive NFC interface of claim 10 wherein the second voltage reducing element comprises a capacitor.

12. A passive NFC interface according to claim 1 or 2 wherein the energy storage module comprises a rectifying unit in parallel with the sensing module and an energy storage unit connected to the rectifying unit, the rectifying unit having an input connected to the sensing module and an output connected to the energy storage unit.

13. The passive NFC interface of claim 12, wherein the energy storage module includes a clipping unit connected between the rectifying unit and the energy storage unit to clip an output voltage of the rectifying unit.

14. The passive NFC interface of claim 12, wherein the energy storage module includes a charge control unit connected between the rectifying unit and the energy storage unit to control the energy storage unit to charge with a small current when a charging parameter of the energy storage unit is less than a parameter threshold and to control the energy storage unit to charge with a large current when the charging parameter is greater than or equal to the parameter threshold.

15. The passive NFC interface of claim 14, including a collection module connected to the control module and the energy storage unit, respectively, for collecting the charging parameters.

16. The passive NFC interface according to claim 14 or 15 wherein the charging parameters include charging time, charging voltage and/or charging power.

17. A passive NFC device comprising a passive NFC interface as claimed in any of claims 1 to 16.

18. The passive NFC device of claim 17, comprising a passive electronic screen, a passive electronic lock, and a passive wearable device.