CN115085770A

CN115085770A - Passive NFC interface and device

Info

Publication number: CN115085770A
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: 2022-09-20
Anticipated expiration: 2041-03-15
Also published as: CN115085770B

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 sensing 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 reduction module is connected with the induction module, and the output end of the voltage reduction 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 invention relates to the technical field of wireless communication, in particular to a passive NFC interface and passive NFC equipment.

Background

Because 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 realized, and the NFC 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, and the like.

Typically, a passive NFC interface is capable of receiving radio frequency energy from an active NFC interface to power itself and an external load. However, the design of the existing passive NFC interface is derived from the RFID technology, the energy receiving efficiency is very 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.

To solve the above technical problem, embodiments of the present invention provide a passive NFC interface and device.

The passive NFC interface provided in the embodiment of the present invention 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 sensing 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 reduction module is connected with the induction module, and the output end of the voltage reduction 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 manner, the pressure differential between the energy storage module and the control module may be increased.

Optionally, the second rf voltage is within an operating voltage interval of the control module.

Optionally, the voltage reduction module and the control module are connected in series and then connected in parallel with the sensing module together.

Optionally, the voltage reduction module comprises at least one set of voltage reduction elements connected between the sensing module and the control module.

Optionally, the control module receives a 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 dropping elements includes a first set of voltage dropping elements and a second set of voltage dropping elements, which are 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 dropping elements comprises at least one first voltage dropping element having a fixed voltage drop.

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

Optionally, the first voltage-dropping element comprises a diode.

Optionally, the diode comprises a light emitting diode.

Optionally, each of the at least one set of voltage dropping elements comprises a second voltage dropping element having an unsteady voltage drop.

Optionally, the second voltage dropping element comprises a capacitor.

Optionally, the energy storage module includes a rectifying unit connected in parallel with the sensing module and an energy storage unit connected to the rectifying unit, an input end of the rectifying unit is connected to the sensing module, and an output end of the rectifying unit is connected to the energy storage unit.

Optionally, the energy storage module includes a limiting unit connected between the rectifying unit and the energy storage unit, so as to limit 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 a charging parameter of the energy storage unit is smaller than a parameter threshold, 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.

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

Optionally, the charging parameter includes a charging time, a charging voltage and/or a charging charge.

The passive NFC device provided in the embodiment of the present invention includes 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 effect.

For example, the first radio-frequency voltage output by the induction module is reduced to the second radio-frequency voltage by the voltage reduction module and is output to the control module, so that the voltage 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.

For another example, the second radio frequency voltage is reduced to the working voltage interval of the control module, so that the amplitude limiting of the first radio frequency voltage output by the induction module by an amplitude limiting circuit in the control module can be avoided, the voltage 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, the voltage reduction module can effectively improve the voltage difference between the energy storage module and the control module to improve the electric energy stored in the energy storage module, so that the passive NFC interface can have a good energy acquisition effect even if one NFC antenna is adopted, the design difficulty of the antenna can be simplified by adopting one NFC antenna, the occupied space of the antenna is reduced to reduce the size of the device, and the cost is saved.

For another example, the diode is used as the voltage-reducing element, which not only has simple circuit design and low cost, but also does not affect the resonant frequency of the sensing module because 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 will change with the change of the electromagnetic field strength, thereby affecting the resonant frequency of the sensing module).

For another example, the light emitting diodes are used, and the voltage drop of the light emitting diodes is large, 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 also be effectively improved by only using one light emitting diode in each group of voltage reduction elements.

For another example, the appropriate distance and relative position between the passive NFC interface and the active NFC device can be quickly found through 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 the energy conversion efficiency is improved.

For another example, when the passive NFC interface supplies power to the load based on the electric energy stored in the energy storage unit to drive the load to act (for example, when the passive electronic lock is unlocked), it may be quickly determined when the load is driven to act (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 example, the capacitor is used as the voltage reduction element, so that not only the circuit design can be simplified, but also the influence on the resonant frequency of the induction module is small because the capacitance value of the capacitor is small.

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 schematic block diagram of a passive NFC interface in an embodiment of the invention.

Detailed Description

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

Different from the prior art, an embodiment of the present invention provides an improved passive NFC interface, including: 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 sensing 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 reduction module is connected with the induction module, and the output end of the voltage reduction 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, according to the passive NFC interface provided by the embodiment of the invention, the voltage reduction module is adopted to reduce the first radio frequency voltage output by the induction module into the second radio frequency voltage and output the second radio frequency voltage to the control module, so that the voltage difference between the energy storage module and the control module and the electric energy stored in the energy storage module can be increased, the loss of radio frequency energy is avoided, the energy conversion efficiency of the passive NFC interface is increased, and the performance and the application range of the passive NFC interface are favorably improved.

In order to make the objects, features and advantages of the embodiments of the present invention more comprehensible, embodiments of the present invention are described in detail below with reference to the accompanying drawings. It is to be understood that the following specific examples are illustrative of the invention and are not to be construed as limiting the invention. In addition, it should be noted that, for convenience of description, only a part of structures related to the present invention, not all of the structures, is shown in the drawings.

In the various figures of the embodiments of the present invention, like modules or portions are identified by like reference numerals.

Referring to fig. 1, a passive NFC interface 101 according to an embodiment of the present invention includes an induction module 110, a voltage-reducing module 120, a control module 130, and a power 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; a voltage-reducing module 120, an input end of which is connected to the sensing module 110 and an output end of which is connected to the control module 130, for receiving and reducing the first rf voltage to form a second rf voltage and outputting the second rf voltage 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 reduction module 120 reduces the first radio frequency voltage output by the sensing module 110 to the second radio frequency voltage and outputs the second radio frequency voltage to the control module 130, so as to increase a voltage difference between the energy storage module 140 and the control module 130, thereby increasing the electric energy stored in the energy storage module 140, and further increasing the energy conversion efficiency of the passive NFC interface 101.

In a specific implementation, the control module 130 may be implemented by using any NFC controller known in the art and having an NFC communication function.

Generally, NFC controllers are provided with a clipping circuit. When the rf voltage output to the NFC controller by the sensing module 110 is greater than the maximum operating voltage of the NFC controller, the amplitude limiting circuit in the NFC controller may discharge the redundant current and limit the rf voltage generated by the sensing module 110, so as to ensure that the NFC controller can operate within the operating voltage range. 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 voltage-reducing module 120, configured to receive the first radio-frequency voltage output by the sensing module 110, and reduce the first radio-frequency voltage into a second radio-frequency voltage to be output to the control module 130. In this way, the amplitude limiting degree of the amplitude limiting circuit in the NFC controller on the first radio frequency voltage output by the sensing module 110 may be reduced to reduce the loss of NFC energy, thereby improving 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 voltage-reducing module 120 may reduce the first rf voltage output by the sensing module 110 to be within an operating voltage interval of the control module 130, that is, to make the second rf voltage be within the operating voltage interval of the control module 130.

Therefore, the amplitude limiting circuit in the NFC controller can be prevented from limiting the first radio frequency voltage output by the sensing module 110 so as to effectively reduce the loss of the NFC energy, thereby improving the energy conversion efficiency of the passive NFC interface 101 and the electric energy stored in the energy storage module 140.

Referring to fig. 2, in a specific 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 constitute a parallel resonant circuit to adjust the resonant frequency of the NFC antenna 111 to its operating frequency of 13.56Hz to optimize the communication effect and the energy reception 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 a specific implementation, the antenna matching unit 112 may be implemented by any conventional technical means known in the art, for example, may be implemented by a matching capacitor connected in parallel with 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 to the rectifying unit 141.

Specifically, the input end of the rectifying unit 141 is connected to the sensing module 110, and the output end thereof is connected to the energy storage unit 122, so as to receive the first radio frequency voltage from the sensing module 110, rectify the first radio frequency voltage, and output the rectified first radio frequency 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 rectified voltage 141, the antenna matching unit 112, and the NFC antenna 111 are connected in parallel.

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

In a specific implementation, the voltage reduction module 120 may include at least one set of voltage reduction elements connected between the sensing 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 the differential rf signal line.

Specifically, the differential rf signal line includes two rf signal lines, i.e., 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 dropping elements includes a first set of voltage dropping elements 121 and a second set of voltage dropping elements 122 connected between the sensing module 110 and the control module 130 through a first rf signal line 131 and a second rf signal line 132, respectively, see fig. 2.

In other embodiments, the control module 130 may also receive the rf signal by using a single non-differential rf signal line, that is, the sensing module 110 and the control module 130 are connected by only one rf signal line.

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

In some embodiments, each set of voltage dropping elements of the at least one set of voltage dropping elements has a fixed voltage drop. In a specific implementation, the first RF voltage is stepped down to form the second RF voltage based on a fixed voltage drop for each set of voltage dropping elements.

In a specific implementation, the fixed voltage drop of each of the at least one set of voltage dropping elements may be determined based on the first rf voltage, the rf voltage expected to be obtained by the energy storage module 140 (which may be obtained based on the electrical energy expected to be obtained by the energy storage module 140), and the operating voltage interval of the control module 130.

For example, to maximize the voltage difference between the energy storage module 140 and the control module 130, and enable the energy storage module 140 to obtain the most power based on the sensing module 110, the second rf voltage may be within the operating voltage range of the control module 130. Given that the first rf voltage is 11V and the operating voltage range of the control module 130 is [4V, 5V ], the fixed voltage drop of each of the at least one set of voltage dropping elements is [6V, 7V ], where 6V-11V-5V and 7V-11V-4V. In this manner, the second rf voltage may be made to be within [4V, 5V ] to maximize the voltage difference between the energy storage module 140 and the control module 130.

The fixed voltage drops of the first group of voltage-dropping elements 121 and the second group of voltage-dropping elements 122 are both at [6V, 7V ] for the aforementioned case of using differential rf signal line connection, and at [6V, 7V ] for the aforementioned case of using single rf signal line connection and only one group of voltage-dropping elements.

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

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

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

In particular, the first voltage-reducing 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 for a red led is about 2 volts, and the voltage drops for a white led and a blue led are about 2.7 volts.

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

In general, the radio frequency energy received by the passive NFC interface 102 is related to the distance and relative position between the passive NFC interface and the active NFC device, and when the distance and relative position between the passive NFC interface and the active NFC device are suitable, 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, the appropriate distance and 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, thereby improving the energy conversion efficiency.

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

Specifically, the second voltage-decreasing element may include a capacitor.

In some embodiments, each set of voltage reduction elements in 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 radio frequency voltage, the radio frequency 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 is not described herein again.

In a specific implementation, the capacitors suitable as the second voltage dropping elements each have a small capacitance value, typically less than 300 picofarads.

In the case of the differential rf signal line connection, one capacitor of the first set of voltage dropping 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 set of voltage dropping 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 set of voltage dropping elements is equal to the capacitance value of one capacitor of the second set of voltage dropping elements.

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

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

Referring to fig. 3, the energy storage module 140 may further include a limiting unit 143 connected between the rectifying unit 141 and the energy storage unit 142, for limiting an output voltage of the rectifying unit 142, so as to ensure that a supply voltage of the energy storage unit 142 to the passive NFC interface 103 and/or the external load does not exceed an operating 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, for controlling 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, and controlling the energy storage unit 142 to perform high current charging when the charging parameter is greater than or equal to the parameter threshold.

In general, the passive NFC interface 103 may not be powered on, fail to communicate, and the like due to an excessive current load at the moment when the passive NFC interface 103 initially enters an electromagnetic field emitted by an 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 communication is stable. When the passive NFC interface 103 is normally powered on and the communication is stable, the energy storage unit 142 may be charged with a large current, so as to improve the charging efficiency.

In the 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 charging control unit 144 may be implemented by any conventional technical means known in the art. For example, the charging control unit 144 may be provided with a current limiting resistor, the charging current of the energy storage unit 142 is limited by the current limiting resistor at the moment of entering the field of the passive NFC interface 103 or when communication is unstable, so as to perform low-current charging, and after communication of the passive NFC interface 103 is stable, the current limiting resistor is cancelled to limit the charging current, so as to perform high-current charging.

In a specific implementation, the charging control unit 144 may be connected between the limiting 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 entering the field or whether communication is stable may be determined based on changes of the charging parameters, such as the charging time, the charging voltage, and the charging amount of the energy storage unit 142, so as to charge the energy storage unit 142 with a small current at the moment of entering the field and when communication is unstable, and charge the energy storage unit 142 with a large current at the moment of communication is stable.

In addition, after the communication of the passive NFC interface 103 is stabilized, it is also possible to select when to perform large-current charging based on the needs of the external load. For example, when the power demand of the external load is large or the 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 communication of the passive NFC interface 103 is stable. In a specific implementation, the time for charging the energy storage unit 142 with the large current may also be determined by the variation of the charging parameters, such as the charging time, the charging voltage, and the charging amount.

In a specific implementation, corresponding parameter thresholds such as a time threshold, a voltage threshold, and a power threshold may be set for charging parameters such as a charging time, a charging voltage, and a charging power, respectively, 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 charging capacity is less than the capacity threshold value, and the energy storage unit 142 is controlled to perform high current charging when the charging capacity is greater than or equal to the capacity threshold value.

In a specific implementation, the control module 130 may be further connected to the charging control unit 144 and the collecting module 150, respectively, for receiving the charging parameter and comparing it with a corresponding parameter threshold, and controlling the charging control unit 144 to charge the energy storage unit 142 with a low current or a high current based on the comparison result.

In an implementation, the control module 130 may be further configured to preset corresponding parameter thresholds.

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

The following description will be made by taking a time threshold as an example.

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

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

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

The embodiment of the present invention further provides a passive NFC device, which includes the

passive NFC interface

101, 102, or 103 provided in the embodiment of the present invention.

In particular, the passive NFC device may include a passive electronic screen, a passive electronic lock, and a passive wearable device.

While specific embodiments have been described above, these embodiments are not intended to limit the scope of the present 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 differently stated. In particular implementations, the features of one or more dependent claims may be combined with those of the independent claims as technically feasible according to the actual requirements, and the features from the respective independent claims may be combined in any appropriate manner and 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 effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A passive NFC interface, comprising:

the NFC device comprises an induction module, a first voltage generation module and a second voltage generation module, wherein the induction module is used for inducing a radio frequency signal emitted by the active NFC device and generating a first radio frequency voltage based on the radio frequency signal;

a control module connected with the sensing module to receive and communicate with the active NFC device 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 reduction module is connected with the induction module, and the output end of the voltage reduction 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.

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. The passive NFC interface according to claim 1 or 2, wherein the voltage-reducing module is connected in series with the control module and then connected in parallel with the sensing module.

4. The passive NFC interface of claim 3, wherein the voltage-dropping module comprises at least one set of voltage-dropping elements connected between the sensing module and the control module.

5. The passive NFC interface of claim 4, wherein the control module receives the radio frequency signal over a differential radio frequency signal line, the differential radio frequency signal line comprising a first radio frequency signal line and a second radio frequency signal line, and wherein the at least one set of voltage dropping elements comprises a first set of voltage dropping elements and a second set of voltage dropping elements connected in series between the sensing module and the control module over 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 voltage dropping elements comprises at least one first voltage dropping element having a fixed voltage drop.

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

8. The passive NFC interface of claim 6, wherein the first voltage-reducing 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 voltage dropping elements comprises a second voltage dropping 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. The passive NFC interface according to claim 1 or 2, wherein the energy storage module comprises a rectifying unit connected in parallel with the sensing module and an energy storage unit connected to the rectifying unit, wherein an input end of the rectifying unit is connected to the sensing module and an output end of the rectifying unit is connected to the energy storage unit.

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

14. The passive NFC interface of claim 12, wherein the energy storage module comprises a charging control unit connected between the rectifying unit and the energy storage unit, and configured to control the energy storage unit to perform low-current charging when a charging parameter of the energy storage unit is smaller than a parameter threshold, 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.

15. The passive NFC interface of claim 14, comprising an acquisition module connected to the control module and the energy storage unit, respectively, for acquiring the charging parameter.

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

17. A passive NFC device characterized in that it comprises a passive NFC interface according to 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.