CN109698713B

CN109698713B - NFC interface with energy management function

Info

Publication number: CN109698713B
Application number: CN201710985842.0A
Authority: CN
Inventors: 周若谷
Original assignee: Hangzhou Qiwei Technology Co ltd
Current assignee: Hangzhou Qiwei Technology Co ltd
Filing date: 2017-10-20
Publication date: 2024-09-06
Anticipated expiration: 2037-10-20

Abstract

The invention discloses an NFC interface with an energy management function, which is provided with an independent energy antenna, and comprises an energy management module and an energy storage module, wherein the energy management module is electrically connected with the energy storage module and is used for charging the energy storage module according to electric energy collected by the energy antenna and also used for cutting off the charging of the energy storage module when the voltage collected by the energy antenna is pulled down to a first voltage threshold value by the energy storage module. The invention can not only greatly improve the energy receiving power of the NFC interface, but also store and manage the electric energy by adding the energy management module to dynamically manage the collected energy, thereby allowing the device with the NFC interface to collect more energy and outputting more NFC energy outwards, and leading the NFC interface to have wider application.

Description

NFC interface with energy management function

Technical Field

The invention relates to the field of wireless communication and wireless charging, in particular to an NFC interface with an energy management function.

Background

NFC (NEAR FIELD Communication) uses a magnetic field as an information carrier, so that a Communication distance (a few centimeters) which is much shorter than that of traditional wireless Communication is realized, and the NFC Communication device has the advantages of high safety, convenience in use and the like. An important part of the NFC standard is the inheritance of the high frequency RFID (Radio Frequency Identification ) passive interface, allowing communication between the NFC reader interface and the NFC passive interface. As shown in fig. 1, the NFC radio frequency signal 104 sent by the NFC reader 101 is given to the NFC passive tag 102. Through the NFC radio frequency signal 104, the NFC reader 101 and the NFC passive tag 102 may implement two-way half duplex communication 105, and one-way wireless energy transmission 103. The NFC passive tag 102 receives radio frequency energy from the NFC reader 101, and rectifies and stabilizes voltage to maintain the internal operation and external communication power supply requirements of the device. However, the design of the conventional NFC passive interface is derived from RFID, and the signal receiving, transmitting and energy coupling are all performed by the same antenna, so that the energy conversion efficiency is low, only a small amount of energy (about 10mW to 20 mW) can be obtained from the NFC reader interface, and only simple operation of the passive device, such as reading and writing the internal memory, can be maintained. At present, the NFC passive interface is widely applied to applications such as wireless payment, bluetooth pairing, peer-to-peer transmission, passive tags, etc., and particularly, the NFC passive interface will be widely applied to applications such as a bank dual interface card, a novel visual bank card, an intelligent wearable device, a sensor network, a future internet of things, etc. which have certain requirements on power consumption, and such low received power will greatly limit functions and performances that can be provided by these applications and applications.

CN105897312a in the prior art has disclosed an NFC tag interface optimized for energy collection and small size, as shown in fig. 2, which includes an antenna 201, an adjustable matching circuit 202, a demodulator 203, an NFC data interface 204, a load modulation circuit 205, a rectifying and voltage stabilizing circuit 206, and an energy collection interface 207, where the adjustable matching circuit 202 can match the antenna 201 to have a low Q value to ensure a communication bandwidth when the antenna 201 realizes data transmission, and has a high Q value when there is no data transmission to allow the rectifying and voltage stabilizing circuit 206 to rectify more electric energy, the NFC data interface 204 transmits NFC data to the outside through a bus after the demodulator 203 demodulates the data, and the energy collection interface 207 transmits electric energy to the outside after collecting the energy. The scheme is that the Q value state of the antenna 201 is changed by the adjustable matching circuit 202 to obtain more energy from the NFC tag interface, which has the disadvantages of complex circuit form, high cost, energy cannot be stored, energy cannot be fully utilized, and the load characteristic of the external device for obtaining NFC energy is required to be continuous and stable, otherwise, the output voltage of the rectifying and voltage stabilizing circuit 206 is pulled down at the moment of abrupt load change (about tens of microseconds), so that the rectifying and voltage stabilizing circuit 206 cannot work normally to influence the normal work of the whole NFC tag interface.

In the prior art, CN105099527a has disclosed a passive NFC communication interface with an independent energy receiving antenna, as shown in fig. 3, the NFC communication interface includes a communication antenna 301, an energy antenna 302, a communication antenna matching circuit 303, an NFC transceiver 304, an energy antenna matching circuit 305, a bridge rectifier 306, and a DC/DC (direct current to direct current) 307, where the communication antenna 301, the communication antenna matching circuit 303, and the NFC transceiver 304 complete NFC transceiver communication and output NFC data outwards, and the energy antenna matching circuit 305, the bridge rectifier 306, and the DC/DC307 complete more energy collection and output NFC energy outwards. This is achieved by adding an antenna, that is, the communication antenna 301 still guarantees a communication bandwidth for a low Q antenna, and the energy antenna 302 independently collects energy for a high Q antenna, so that more energy is obtained, but the disadvantage is that energy cannot be stored, energy cannot be fully utilized, and the load characteristic of an external device for obtaining NFC energy is required to be continuous and stable, otherwise, the output voltage of the DC/DC circuit 307 will be pulled down at the moment of sudden load change (about tens of microseconds), so that the DC/DC circuit 307 cannot work normally and the normal operation of the whole NFC communication interface is affected.

Disclosure of Invention

The invention aims to overcome the defects that the energy conversion efficiency of the traditional NFC interface with a single antenna is low or the energy conversion efficiency is improved through matching adjustment in the prior art, but the complexity and the cost of a circuit are increased, the energy cannot be fully utilized and the normal operation of an energy conversion circuit cannot be effectively ensured, and the NFC interface adopting an independent energy antenna cannot fully utilize the energy and the normal operation of the energy conversion circuit can be effectively ensured although more energy can be obtained.

The invention solves the technical problems by the following technical scheme:

The invention provides an NFC interface with an energy management function, which is provided with an independent energy antenna and is characterized by comprising an energy management module and an energy storage module, wherein the energy management module is electrically connected with the energy storage module, and is used for charging the energy storage module according to electric energy collected by the energy antenna and cutting off charging the energy storage module when the voltage collected by the energy antenna is pulled down to a first voltage threshold value by the energy storage module.

In this scheme, can gather more energy through adopting independent energy antenna at first, then store energy in the energy storage module effectively through energy management module to improve energy utilization efficiency. However, since the energy storage module has extremely low ESR (Equivalent series resistance), the impedance is very low during charging, and a large charging current is required, particularly, the energy storage module generally pulls down the input voltage value instantaneously (for example, for a period of several tens of microseconds) in the initial period of power-up, so that the power supply voltage of other circuits is too low to work normally. Therefore, the energy management module is required to dynamically manage the charging of the energy storage module according to the electric energy collected by the energy antenna, and the energy management module is required to respond quickly in the charging management process, namely, when the voltage collected by the energy antenna is pulled down to a first voltage threshold value by the energy storage module, the charging is cut off in time, so that the electric energy collected by the energy antenna can be recovered to a normal value, and the energy storage module can be ensured to be charged, and the voltage cannot be pulled down too much to influence the normal operation of other circuits. The specific value of the first voltage threshold should be generally configured according to practical application requirements to meet different application requirements, but should generally be between 3.3V and 10V.

Preferably, the energy management module comprises a charging switch, the charging switch is electrically connected with the energy storage module, and the energy management module is further used for controlling the on and off of the charging switch. Among them, the charge switch can preferably have a device with small on-resistance and a fast response speed, such as a MOSFET (metal-oxide semiconductor field effect transistor), so that the charge switch can be ensured to have a fast response speed.

Preferably, the charging switch further comprises a charging inhibition control end, and the charging inhibition control end is used for forcibly turning off the charging switch. The charging inhibition end can enable the NFC interface to forcibly turn off the charging switch so as to timely and reliably protect the NFC interface.

Preferably, the energy management module further includes a first voltage comparator and a first voltage configuration circuit, the first voltage configuration circuit is configured to generate the first voltage threshold, two input ends of the first voltage comparator respectively input the first voltage threshold and the electric energy collected by the energy antenna, an output end of the first voltage comparator is electrically connected with the charging switch, and the first voltage comparator is configured to output a turn-on signal to the charging switch when the voltage of the electric energy collected by the energy antenna is higher than the first voltage threshold, otherwise, output a turn-off signal to the charging switch.

In the scheme, the electric energy collected by the energy antenna is judged through the first voltage comparator, and when the collected electric energy is higher than a first voltage threshold value, a conduction signal is generated to conduct the charging switch, so that the energy management module charges the energy storage module with the electric energy through the charging switch; otherwise, the charging switch is turned off by outputting the turn-off signal, so that the energy management module stops charging the energy storage module with electric energy to ensure the normal operation of other circuits.

Preferably, the energy management module further comprises a discharge switch, the energy storage module is electrically connected with an external load through the discharge switch, and the energy management module is further used for controlling on and off of the discharge switch. The energy management module charges the energy storage module with the electric energy collected by the energy antenna and simultaneously supplies the electric energy to an external load through a discharge switch; when only the energy storage module stores energy, the energy management module discharges the electric energy stored by the energy storage module to an external load through the discharge switch; the discharge switch can be preferably a device with small on-resistance and high response speed, such as a MOSFET, so that the discharge switch can be ensured to have high response speed.

Preferably, the response time of the charge switch is less than 10 μs and/or the response time of the discharge switch is less than 10 μs.

Preferably, the energy management module further includes a second voltage comparator and a second voltage configuration circuit, the second voltage configuration circuit is configured to generate a second voltage threshold, two input ends of the second voltage comparator respectively input the second threshold voltage and the electric energy of the energy storage module, an output end of the second voltage comparator is electrically connected with the discharge switch, and the second voltage comparator is configured to output a turn-off signal to the discharge switch when a voltage value of the electric energy stored by the energy storage module is lower than the second voltage threshold. The specific value of the second voltage threshold should be generally configured according to practical application requirements to meet different application requirements, but should generally be between 2.4V and 5V.

Preferably, the energy management module further includes a third voltage comparator and a third voltage configuration circuit, the third voltage configuration circuit is configured to generate a third voltage threshold, the second voltage threshold is lower than the third voltage threshold, two input ends of the third voltage comparator respectively input the third voltage threshold and the electric energy of the energy storage module, the third voltage comparator is configured to output an alarm signal when the voltage value of the electric energy stored by the energy storage module is lower than the third voltage threshold, and the NFC interface is configured to discharge and alarm to an external load according to the alarm signal. The second voltage threshold should be lower than the third voltage threshold, and the specific value of the third voltage threshold should be generally configured according to practical application requirements to meet different application requirements, but should generally be between 3.3V and 7V.

Preferably, propagation delay times of the first voltage comparator, the second voltage comparator and the third voltage comparator are all smaller than 5 μs. The first voltage comparator, the second voltage comparator and the third voltage comparator can be high-speed analog comparators with small propagation delay time, so that the comparators can be guaranteed to output signals in time.

Preferably, the NFC interface further includes an antenna matching circuit, where the antenna matching circuit is configured to match the energy antenna to improve energy receiving efficiency. The energy conversion efficiency of the energy antenna can be further improved through the antenna matching circuit, so that more electric energy can be acquired through the energy antenna.

Preferably, the NFC interface further includes an independent receiving antenna, an independent transmitting antenna, a demodulation module, a load modulation module, and an NFC controller, where the receiving antenna is electrically connected with the demodulation module, the transmitting antenna is electrically connected with the load modulation module, the NFC controller is electrically connected with the demodulation module and the load modulation module, the receiving antenna is used to receive NFC signals transmitted by the NFC reader and send the NFC signals to the demodulation module, the demodulation module demodulates and then transmits demodulation data to the NFC controller, and the NFC controller is used to transmit data to be transmitted to the load modulation module according to a predetermined format, and the NFC controller modulates the data and then sends the NFC signals to the NFC reader through the transmitting antenna.

In this scheme, the receiving antenna, the demodulation module, and the NFC controller form an NFC receiving channel, and the NFC controller, the load modulation module, and the transmitting antenna form an NFC transmitting channel, where the receiving antenna and the transmitting antenna may use antennas with low Loaded Q-factor (also called Loaded Q-factor) when the receiving antenna and the transmitting antenna are near the frequency of 13.56MHz, and such antennas may ensure sufficient communication bandwidth. In addition, if the antenna itself cannot provide a low Q value with load, a matching circuit may be used to reduce the Q value with load by matching. The number of turns of the receiving antenna is small, and when the receiving antenna is communicated with a common NFC reader-writer, the induced voltage is low (for example, the peak-to-peak value Vpp is smaller than 1.5V), and the voltage can be directly used for signal processing and demodulation in a common CMOS (Complementary Metal Oxide Semiconductor ) device without conversion. Meanwhile, the lower voltage means that NFC radio frequency energy consumed by the signal receiving circuit is lower, and the energy receiving efficiency is improved. The loaded Q values of the low load state and the high load state of the transmitting antenna are generally controlled to be between 5 and 20. The load modulation module generally has a very low internal resistance (e.g., less than 10Ω) for improving the signal strength of the transmission in the high-load state.

Preferably, the NFC interface further includes an independent communication antenna, a demodulation module, a load modulation module, and an NFC controller, where the communication antenna is electrically connected with the demodulation module and the load modulation module, the communication antenna receives an NFC signal emitted by the NFC card reader and sends the NFC signal to the demodulation module, the demodulation module demodulates and then transmits demodulation data to the NFC controller, and the NFC controller is configured to transmit data to be sent to the load modulation module according to a predetermined format, and after modulated by the load modulation module, send the NFC signal to the NFC card reader through the communication antenna.

Preferably, the NFC interface further includes a data buffering module and a bus interface module, where the data buffering module is electrically connected with the NFC controller and the bus interface module, the bus interface module is electrically connected with an external load, the data buffering module is used for buffering NFC data exchanged between the NFC controller and the external load, and the bus interface module is used for communicating NFC data with the external load. Wherein the bus interface module comprises a common serial data bus interface.

Preferably, the NFC interface further includes a carrier recovery module, where the carrier recovery module is electrically connected to the energy antenna or the receiving antenna, and the carrier recovery module is configured to recover an NFC carrier signal from electric energy collected by the corresponding energy antenna or the receiving antenna.

In the scheme, the carrier recovery module recovers the clock required by load modulation from the NFC radio frequency signal, so that an expensive crystal oscillator is omitted, the cost and the volume are greatly reduced, and higher clock precision and stability can be provided for the load modulation.

Preferably, the carrier recovery module includes a dc blocking bias circuit and a fourth voltage comparator, where the energy antenna or the receiving antenna is a differential antenna, two input ends of the fourth voltage comparator are electrically connected with the differential antenna through the dc blocking bias circuit, the dc blocking bias circuit is used to generate a dc bias voltage, the dc bias voltage is used to provide the same dc bias for the two input ends of the fourth voltage comparator, the dc blocking bias circuit is further used to transmit an ac differential signal collected by the differential antenna to the fourth voltage comparator, and dc isolate the differential antenna, and the fourth voltage comparator is used to output a recovered NFC carrier signal. The dc bias voltage is generally preferably half of the power supply voltage of the fourth voltage comparator, so as to provide the most suitable bias for the ac signal at the input end of the comparator, so that the peak-to-peak amplitude of the ac signal can reach the power supply voltage at the maximum, and the positive half cycle and the negative half cycle of the ac signal are symmetrical as much as possible.

Preferably, the dc bias circuit includes a first blocking capacitor, a second blocking capacitor, a first resistor, a second resistor and a bias voltage generator, one end of the first blocking capacitor is connected to one end of the differential antenna, the other end of the first blocking capacitor is connected to one end of the first resistor and one input end of the fourth voltage comparator, one end of the second blocking capacitor is connected to the other end of the differential antenna, the other end of the second blocking capacitor is connected to one end of the second resistor and the other input end of the fourth voltage comparator, the other end of the first resistor and the other end of the second resistor are connected to the output end of the bias voltage generator, and the bias voltage generator is used for generating and outputting the dc bias voltage.

Preferably, the NFC interface further includes a rectifying module and a voltage stabilizing module, where the rectifying module is electrically connected to the energy antenna, the voltage stabilizing module, and the energy management module is further electrically connected to an external load; the rectification module is used for rectifying the electric energy collected by the energy antenna, generating direct-current electric energy and then outputting the direct-current electric energy to the voltage stabilizing module and the energy management module respectively; the voltage stabilizing module is used for stabilizing the direct-current electric energy and providing a working power supply for the NFC interface; the energy management module is used for charging the energy storage module according to the direct-current electric energy and discharging the energy storage module to an external load according to the electric energy stored by the energy storage module.

Preferably, the rectifying module comprises a diode rectifying bridge, the diode voltage drop of the diode in the diode rectifying bridge is smaller than 1V when the conducting current is 20mA, and/or the voltage stabilizing module comprises a linear voltage stabilizer or a switching voltage stabilizer, and the output voltage range of the voltage stabilizing module is 1.7V-3.6V.

Preferably, the energy storage module comprises an energy storage capacitor.

Preferably, the capacitance value of the energy storage capacitor is 22 mu F-0.47F. The withstand voltage of the capacitor is generally determined according to the antenna coupling characteristics, but is generally 9V or more. In addition, in order to reduce the ESR of the capacitor to improve the storage efficiency, a mode in which a plurality of capacitors are connected in parallel may be adopted.

The invention has the positive progress effects that: the invention can not only greatly improve the energy receiving power of the NFC interface, but also store and manage the electric energy by adding the energy management module so as to allow the device with the NFC interface to collect more energy and output more NFC energy outwards, so that the NFC interface is more widely popularized to various applications, the device can provide more application functions, the application performance is improved, and a user can obtain better experience.

Drawings

Fig. 1 is a schematic diagram of a conventional NFC passive tag in communication with an NFC reader.

Fig. 2 is a schematic diagram of the composition of an NFC tag interface optimized for energy harvesting and small size in the prior art.

Fig. 3 is a schematic diagram of a passive NFC communication interface with a separate energy receiving antenna in the prior art.

Fig. 4 is a schematic diagram of the composition of an NFC interface with energy management function according to embodiment 1 of the present invention.

Fig. 5 is a schematic diagram of the composition of an energy management module of an NFC interface with energy management function according to embodiment 1 of the present invention.

Fig. 6 is a schematic diagram illustrating a carrier recovery module of an NFC interface with energy management function according to embodiment 1 of the present invention.

Fig. 7 is a schematic diagram of the composition of an NFC interface with energy management function according to embodiment 2 of the present invention.

Detailed Description

The invention is further illustrated by means of the following examples, which are not intended to limit the scope of the invention.

Example 1

The present embodiment relates to an NFC interface with an energy management function, as shown in fig. 4, where the NFC interface has an independent energy antenna 401, and the NFC interface includes an energy management module 402 and an energy storage module 403, where the energy management module 402 is electrically connected to the energy storage module 403, and the energy management module 402 is configured to charge the energy storage module 403 according to electric energy collected by the energy antenna 401 (e.g. "electric energy to be stored" shown in fig. 4), and further configured to cut off charging of the energy storage module 403 when the voltage collected by the energy antenna 401 is pulled down to a first voltage threshold by the energy storage module 403. In specific implementation, the energy storage module 403 may preferably be an energy storage capacitor, the capacitance value of the energy storage capacitor may be preferably in the range of 22 μf to 0.47F, the specific capacitance value may be selected according to actual needs, the larger the capacitance, the more the electric energy can be stored, the better the smoothing effect, but the longer the charging time when power is on, and the longer the waiting time for the user. The withstand voltage of the capacitor is generally determined according to the coupling characteristic of the energy antenna 401, but is generally 9V or more. In addition, to reduce the ESR of the capacitor to improve the storage efficiency, the energy storage module 403 may be configured by a plurality of capacitors connected in parallel. In addition, since the capacitor has an extremely low ESR, the capacitor will typically pull the input voltage value low instantaneously (e.g., tens of microseconds long) during the power-up initiation phase, thereby causing the supply voltage of other circuits to be too low to operate properly. Therefore, the energy management module 402 is required to have a fast response characteristic in energy transmission, that is, when the energy storage module 403 pulls down the voltage collected by the energy antenna 401 to the first voltage threshold, the charging of the energy storage module 403 is cut off, so as to ensure that the capacitor does not pull down the voltage too low to affect the normal operation of other circuits at the moment of power-up.

Further, in the implementation of this embodiment, as shown in fig. 5, the energy management module 402 includes a charging switch 4021, where the charging switch 4021 is electrically connected to the energy storage module 403, and the energy management module 402 is further configured to control on and off of the charging switch 4021, and charge the energy storage module 403 if the charging switch 4021 is turned on, and cut off charging the energy storage module 403 if the charging switch 4021 is turned off. In a specific implementation, the energy management module 402 further includes a first voltage comparator U1 and a first voltage configuration circuit 4022, where the first voltage configuration circuit 4022 is configured to generate a first voltage threshold, two input ends of the first voltage comparator U1 respectively input the first voltage threshold and electric energy collected by the energy antenna 401 (as "electric energy to be stored" shown in fig. 5), an output end of the first voltage comparator U1 is electrically connected to the charging switch 4021, and the first voltage comparator U1 is configured to output an on signal to the charging switch 4021 when a voltage of the electric energy collected by the energy antenna 401 is higher than the first voltage threshold, and otherwise output an off signal to the charging switch 4021. This ensures that the voltage collected by the energy antenna 401 is always higher than the first voltage threshold, ensuring that the system is powered stably.

Further, in this embodiment, the charging switch 4021 further includes a charging prohibition control terminal for forcibly turning off the charging switch 4021 when there is a charging prohibition signal. The charge inhibition control end can force the NFC interface to turn off the charge switch, so as to timely and reliably protect the NFC interface, for example, when the NFC interface is receiving and transmitting NFC radio frequency signals, in order to avoid interference with the receiving and transmitting, the charge inhibition control end can temporarily suspend the charge of the energy storage module 403.

Further, in this embodiment, the energy management module 402 further includes a discharge switch 4023, the energy storage module 403 is electrically connected to an external load (the external load is not shown in the figure) through the discharge switch 4023, and the energy management module 402 is further configured to control on and off of the discharge switch 4023, discharge to the external load if the discharge switch 4023 is on, and stop discharge to the external load if the discharge switch 4023 is off. The energy management module 402 charges the energy storage module 403 with the electric energy collected by the energy antenna 401 and simultaneously supplies the electric energy to an external load through the discharge switch 4023; when only the energy of the energy storage module 403 is stored, the energy management module 402 discharges the electric energy stored in the energy storage module 403 to an external load through the discharge switch 4023.

Further, in this embodiment, the energy management module 402 further includes a second voltage comparator U2 and a second voltage configuration circuit 4024, the second voltage configuration circuit 4024 is configured to generate a second voltage threshold, two input ends of the second voltage comparator U2 are respectively input with the second threshold voltage and the electric energy of the energy storage module 403, an output end of the second voltage comparator U2 is electrically connected to the discharge switch 4023, and the second voltage comparator U2 is configured to output an off signal to the discharge switch 4023 when the voltage value of the electric energy stored in the energy storage module 403 is lower than the second voltage threshold. In addition, the energy management module 402 may output the off signal, where the NFC interface may learn the off signal, so as to learn an internal state, so as to perform interface management, such as resetting some internal states of the NFC interface, so that the NFC interface may wake up immediately when power is restored.

Further, in this embodiment, the energy management module 402 further includes a third voltage comparator U3 and a third voltage configuration circuit 4025, where the third voltage configuration circuit 4025 is configured to generate a third voltage threshold, the second voltage threshold is lower than the third voltage threshold, two input ends of the third voltage comparator U3 respectively input the third voltage threshold and the electric energy of the energy storage module 403, the third voltage comparator U3 is configured to output an alarm signal when the voltage value of the electric energy stored in the energy storage module 403 is lower than the third voltage threshold, and the NFC interface is configured to perform a discharge alarm to an external load according to the alarm signal, so that an alarm is given before stopping discharging to the external load, so that the external load immediately reduces energy consumption, so that the external load can process and store data in time.

In implementation of this embodiment, the charging switch 4021 and the discharging switch 4023 may preferably have devices with small on-resistance and fast response speed, such as MOSFETs, so that the response speed of the switches is ensured to be faster, and the response time of the switches should be less than 10 μs.

In the implementation of this embodiment, the first voltage comparator U1, the second voltage comparator U2 and the third voltage comparator U3 may be high-speed analog comparators with small propagation delay time, so that the comparators can output signals in time, and the propagation delay time of the comparators should be less than 5 μs.

In the implementation of this embodiment, the first voltage configuration circuit 4022, the second voltage configuration circuit 4024 and the third voltage configuration circuit 4025 may be configured from the outside of the energy management module 402 when generating the corresponding voltage thresholds, that is, the NFC interface may correspondingly implement the configurations of the first voltage threshold, the second voltage threshold and the third voltage threshold by configuring the parameters of the first voltage configuration circuit 4022, the second voltage configuration circuit 4024 and the third voltage configuration circuit 4025, so that the NFC interface is convenient to configure the corresponding voltage thresholds according to actual needs. Wherein the first voltage threshold should generally be between 3.3V and 10V; the second voltage threshold should typically be between 2.4V and 5V; the third voltage threshold should typically be between 3.3V and 7V. Of course, the second voltage threshold should also be lower than the third voltage threshold.

Further, in this embodiment, the NFC interface further includes an independent receiving antenna 407, an independent transmitting antenna 408, a demodulating module 409, a load modulating module 411, and an NFC controller 410, where the receiving antenna 407 is electrically connected with the demodulating module 409, the transmitting antenna 408 is electrically connected with the load modulating module 411, the NFC controller 410 is respectively electrically connected with the demodulating module 409 and the load modulating module 411, the receiving antenna 407 is configured to receive an NFC signal transmitted by the NFC reader and send the NFC signal to the demodulating module 409, the demodulating module 409 demodulates the NFC signal and then transmits the demodulated data to the NFC controller 410, the NFC controller 410 is configured to package the data to be transmitted to the load modulating module 411 according to a predetermined format, and the NFC signal is modulated by the load modulating module 411 and then sent to the NFC reader through the transmitting antenna 408. Therefore, the receiving antenna 407, the demodulation module 409 and the NFC controller 410 form an NFC receiving channel, while the NFC controller 410, the load modulation module 411 and the transmitting antenna 408 form an NFC transmitting channel, and when the receiving antenna 407 and the transmitting antenna 408 are near the frequency of 13.56MHz, an antenna with a lower Q value (Loaded Q-factor) can be used, and such an antenna can ensure a sufficient communication bandwidth. In addition, if the antenna itself cannot provide a low Q value with load, a matching circuit (not identified in the matching circuit diagram herein) may also be used to reduce the Q value with load by matching. The number of turns of the receiving antenna 407 is small, and when the receiving antenna communicates with a common NFC reader-writer, the induced voltage is low (for example, the peak-to-peak value Vpp is less than 1.5V), and the voltage can be directly used for signal processing and demodulation in a common CMOS device without conversion. Meanwhile, the lower voltage means that NFC radio frequency energy consumed by the signal receiving circuit is lower, and the energy receiving efficiency is improved. The loaded Q values of the low load and high load states of the transmit antenna 408 are typically controlled to be between 5-20. The load modulation module 411 generally has a very low on internal resistance (e.g., less than 10Ω), which is advantageous for improving the transmission signal strength in the high load state.

Further, in this embodiment, the NFC interface further includes a data buffer module 413 and a bus interface module 414, where the data buffer module 413 is electrically connected to the NFC controller 410 and the bus interface module 414, the bus interface module 414 is electrically connected to an external load (not identified in the drawing), the data buffer module 413 is used to buffer NFC data exchanged between the NFC controller 410 and the external load, and the bus interface module 414 is used to communicate NFC data with the external load, where the NFC data generally includes changing one or several configurations of the NFC interface, reading and writing internal memory contents of the NFC interface, transmitting data to be sent, retrieving received data, and so on.

Further, in this embodiment, the NFC interface further includes a carrier recovery module 412, where the carrier recovery module 412 is electrically connected to the receiving antenna 407, and the carrier recovery module 412 is configured to recover the NFC carrier signal from the electrical energy collected by the receiving antenna 407. At this time, the carrier recovery module 412 recovers a clock signal from the NFC radio frequency signal, the clock signal is used to drive the logic in the NFC controller 410, and control the timing sequence of receiving and transmitting, so that the clock signal can be synchronized with the timing sequence of the NFC reader-writer, and the original expensive crystal oscillator can be omitted, thereby greatly reducing the cost and the volume, and providing higher clock precision and stability.

Further, in the embodiment, as shown in fig. 6, the carrier recovery module 412 includes a dc blocking bias circuit 4121 and a fourth voltage comparator U4, where the power supply of the carrier recovery module 412 is VDD, the receiving antenna 407 is a differential antenna, two input ends of the fourth voltage comparator U4 are electrically connected to the antenna through the dc blocking bias circuit 4121, respectively, the dc blocking bias circuit 4121 is used to generate a dc bias voltage, the dc bias voltage is used to provide the same reference voltage to the two input ends of the fourth voltage comparator U4 as a dc bias, the dc blocking bias circuit 4121 is further used to transmit the ac differential signal collected by the antenna to the fourth voltage comparator U4, and perform dc isolation on the antenna, and the output end of the fourth voltage comparator U4 obtains the carrier signal with 13.56Mhz of the modulation removed, that is, i.e., the recovered NFC carrier signal. The dc bias voltage is generally preferably half of the power supply voltage of the fourth voltage comparator, so as to provide the most suitable bias for the ac signal at the input end of the comparator, so that the peak-to-peak amplitude of the ac signal can reach the power supply voltage at the maximum, and the positive half cycle and the negative half cycle of the ac signal are symmetrical and undistorted as much as possible. In a specific implementation, the blocking bias circuit 4121 includes a first blocking capacitor C1, a second blocking capacitor C2, a first resistor R1, a second resistor R2, and a bias voltage generator 41211, where one end of the first blocking capacitor C1 is connected to one end of the receiving antenna 407, the other end of the first blocking capacitor C1 is connected to one end of the first resistor R1 and one input end of the fourth voltage comparator U4, one end of the second blocking capacitor C2 is connected to the other end of the receiving antenna 407, the other end of the second blocking capacitor C2 is connected to one end of the second resistor R2 and the other input end of the fourth voltage comparator U4, the other end of the first resistor R1 and the other end of the second resistor R2 are both connected to the output end of the bias voltage generator 41211, and the bias voltage generator 41211 is used for generating and outputting the dc bias voltage.

Further, in this embodiment, the NFC interface further includes an energy antenna matching circuit 404, a rectifying module 405 and a voltage stabilizing module 406, where the energy antenna matching circuit 404 is configured to match the energy antenna 401 to improve energy receiving efficiency, the rectifying module 405 is electrically connected to the energy antenna matching circuit 404, the voltage stabilizing module 406 and the energy management module 402, and the energy management module 402 is further electrically connected to an external load; the rectifying module 405 is configured to rectify the electric energy collected by the energy antenna 401, generate dc electric energy, and output the dc electric energy to the voltage stabilizing module 406 and the energy management module 402, respectively; the voltage stabilizing module 406 is configured to stabilize the dc power and provide a working power supply for the NFC interface; the energy management module 402 is configured to charge the energy storage module 403 according to the dc electrical energy (the "electrical energy to be stored" as shown in fig. 4), and is further configured to discharge to an external load according to the electrical energy stored by the energy storage module 403. In the implementation, the energy antenna matching circuit 404 may be selected according to the actual implementation, if the characteristics of the energy antenna are enough to collect energy, the energy antenna matching circuit 404 may be omitted to save cost and volume; the rectifying module 405 includes a diode rectifying bridge, where a diode voltage drop of the diode in the diode rectifying bridge is less than 1V when the conducting current is 20mA, and a low tube voltage drop is beneficial to reduce energy consumption. In addition, the voltage stabilizing module 406 includes a linear voltage stabilizer or a switching voltage stabilizer, the output voltage range of the voltage stabilizing module 406 is 1.7V-3.6V, and the specific voltage value can be designed according to the power supply requirement of the NFC interface.

In order to facilitate the visual understanding of the practical effect of the present invention, the following is that energy receiving measurement is performed on the NFC interface with energy management function related to embodiment 1, and by comparing the NFC interface with energy management function of embodiment 1 with the conventional NFC tag interface, an energy collecting test is performed, wherein a mobile phone with NFC function is used as a conventional NFC reader, and the size of the energy antenna in embodiment 1 is the same as that of the conventional NFC tag for testing, and the test comparison result is shown in table 1.

Table 1 test results

Mobile phone model	NFC interface of the present embodiment	Traditional NFC tag
			Samsung Galaxy S4	65mW	10mW
Hua is Mate9	120mW	15mW
			Apple iPhone7 (iOS 11)	100mW	17mW
Knoop-Biya	220mW	27mW

Test results show that under the same test conditions, the NFC interface with energy management function related to embodiment 1 can collect much more energy than the conventional NFC tag, and the results show that the NFC interface with energy management function related to embodiment 1 can collect energy more effectively.

Example 2

The NFC interface with energy management function according to this embodiment is substantially the same as that of embodiment 1, and is different in that, as shown in fig. 7, the NFC interface uses an independent communication antenna 415 to replace the receiving antenna 407 and the transmitting antenna 408 in embodiment 1, where the communication antenna 415 is electrically connected to the demodulation module 409 and the load modulation module 411, and the energy antenna 401 is connected to the carrier recovery module 412 and the energy antenna matching circuit 404, respectively, so that a pair of antennas can be simplified, and the cost and the volume can be further reduced. In view of the above differences, embodiment 2 is substantially the same as embodiment 1, and the remainder of this description will be omitted. In addition, since the voltage value induced by the energy antenna 401 is generally higher, in implementation, the carrier recovery module 412 needs to reduce the higher voltage and then supply power to the common CMOS circuit, and the voltage reduction can be generally achieved by resistor or capacitor voltage division, which is not described herein.

While specific embodiments of the invention have been described above, it will be appreciated by those skilled in the art that this is by way of example only, and the scope of the invention is defined by the appended claims. Various changes and modifications to these embodiments may be made by those skilled in the art without departing from the principles and spirit of the invention, but such changes and modifications fall within the scope of the invention.

Claims

1. The NFC interface is provided with an independent energy antenna, and is characterized by comprising an energy management module and an energy storage module, wherein the energy management module is electrically connected with the energy storage module, and is used for charging the energy storage module according to electric energy collected by the energy antenna and also used for cutting off charging the energy storage module when the voltage collected by the energy antenna is pulled down to a first voltage threshold value by the energy storage module; the energy management module further comprises a charging switch, a first voltage comparator and a first voltage configuration circuit, wherein the first voltage configuration circuit is used for generating a first voltage threshold, two input ends of the first voltage comparator are respectively used for inputting the first voltage threshold and electric energy collected by the energy antenna, the output end of the first voltage comparator is electrically connected with the charging switch, and the first voltage comparator is used for outputting a conduction signal to the charging switch when the voltage of the electric energy collected by the energy antenna is higher than the first voltage threshold, and otherwise outputting a turn-off signal to the charging switch.

2. The NFC interface with energy management function of claim 1, wherein the charging switch further comprises a charge inhibit control terminal for forcibly turning off the charging switch.

3. The NFC interface with energy management function of claim 1, wherein the energy management module further comprises a discharge switch through which the energy storage module is electrically connected to an external load, the energy management module further configured to control on and off of the discharge switch.

4. An NFC interface with energy management function according to claim 3 wherein the response time of the charge switch is less than 10 μs and/or the response time of the discharge switch is less than 10 μs.

5. The NFC interface with energy management function of claim 3, wherein the energy management module further includes a second voltage comparator and a second voltage configuration circuit, the second voltage configuration circuit is configured to generate a second voltage threshold, two input terminals of the second voltage comparator respectively input the second voltage threshold and the energy of the energy storage module, an output terminal of the second voltage comparator is electrically connected to the discharge switch, and the second voltage comparator is configured to output an off signal to the discharge switch when a voltage value of the energy stored by the energy storage module is lower than the second voltage threshold, and otherwise output an on signal to the discharge switch.

6. The NFC interface with energy management function of claim 5, wherein the energy management module further includes a third voltage comparator and a third voltage configuration circuit, the third voltage configuration circuit configured to generate a third voltage threshold, the second voltage threshold being lower than the third voltage threshold, two input terminals of the third voltage comparator respectively input the third voltage threshold and the energy of the energy storage module, the third voltage comparator configured to output an alarm signal when a voltage value of the energy stored in the energy storage module is lower than the third voltage threshold, and the NFC interface configured to discharge an alarm to an external load according to the alarm signal.

7. The NFC interface with energy management function of claim 6, wherein propagation delay times of the first voltage comparator, the second voltage comparator, and the third voltage comparator are each less than 5 μs.

8. The NFC interface with energy management function of claim 1, further comprising an antenna matching circuit for matching the energy antenna to improve energy reception efficiency.

9. The NFC interface with energy management function of claim 1, further comprising an independent receive antenna, an independent transmit antenna, a demodulation module, a load modulation module, and an NFC controller, wherein the receive antenna is electrically connected to the demodulation module, the transmit antenna is electrically connected to the load modulation module, and the NFC controller is electrically connected to the demodulation module and the load modulation module, respectively;

The receiving antenna is used for receiving NFC signals transmitted by the NFC card reader and sending the NFC signals to the demodulation module, and the demodulation module demodulates the NFC signals and then transmits demodulated data to the NFC controller;

The NFC controller is used for transmitting data to be transmitted to the load modulation module according to a preset format, and the NFC controller is used for transmitting NFC signals to the NFC card reader through the transmitting antenna after being modulated by the load modulation module.

10. The NFC interface with energy management function of claim 1, further comprising an independent communication antenna, a demodulation module, a load modulation module, and an NFC controller, wherein the communication antenna is electrically connected to the demodulation module and the load modulation module, respectively;

The communication antenna is used for receiving NFC signals transmitted by the NFC card reader and sending the NFC signals to the demodulation module, and the demodulation module demodulates the NFC signals and then transmits demodulated data to the NFC controller;

The NFC controller is used for transmitting data to be transmitted to the load modulation module according to a preset format, and the NFC controller is used for transmitting NFC signals to the NFC card reader through the communication antenna after being modulated by the load modulation module.

11. The NFC interface with energy management function according to claim 9 or 10, wherein the NFC interface further comprises a data buffering module and a bus interface module, the data buffering module is electrically connected with the NFC controller and the bus interface module, the bus interface module is electrically connected with an external load, the data buffering module is used for buffering NFC data exchanged between the NFC controller and the external load, and the bus interface module is used for communicating NFC data with the external load.

12. The NFC interface with energy management function of claim 9, further comprising a carrier recovery module electrically connected to the energy antenna or the receiving antenna, the carrier recovery module configured to recover an NFC carrier signal from electrical energy collected by the respective energy antenna or receiving antenna.

13. The NFC interface with energy management function of claim 12, wherein the carrier recovery module includes a dc blocking bias circuit and a fourth voltage comparator, the energy antenna or the receiving antenna is a differential antenna, two input terminals of the fourth voltage comparator are electrically connected to the differential antenna through the dc blocking bias circuit, the dc blocking bias circuit is configured to generate a dc bias voltage, the dc bias voltage is configured to provide the same dc bias for the two input terminals of the fourth voltage comparator, the dc blocking bias circuit is further configured to transmit an ac differential signal collected by the differential antenna to the fourth voltage comparator, and dc isolate the differential antenna, and the fourth voltage comparator is configured to output a recovered NFC carrier signal.

14. The NFC interface with energy management function according to claim 13, wherein the dc bias circuit includes a first blocking capacitor, a second blocking capacitor, a first resistor, a second resistor, and a bias voltage generator, one end of the first blocking capacitor is connected to one end of the differential antenna, the other end of the first blocking capacitor is connected to one input end of the first resistor and one input end of the fourth voltage comparator, one end of the second blocking capacitor is connected to the other end of the differential antenna, the other end of the second blocking capacitor is connected to one end of the second resistor and the other input end of the fourth voltage comparator, and the other end of the first resistor and the other end of the second resistor are both connected to an output end of the bias voltage generator, and the bias voltage generator is configured to generate and output the dc bias voltage.

15. The NFC interface with energy management function according to claim 1, further comprising a rectifying module and a voltage stabilizing module, wherein the rectifying module is electrically connected to the energy antenna, the voltage stabilizing module, and the energy management module, respectively, and the energy management module is further electrically connected to an external load;

the rectification module is used for rectifying the electric energy collected by the energy antenna, generating direct-current electric energy and then outputting the direct-current electric energy to the voltage stabilizing module and the energy management module respectively;

the voltage stabilizing module is used for stabilizing the direct-current electric energy and providing a working power supply for the NFC interface;

the energy management module is used for charging the energy storage module according to the direct-current electric energy and discharging the energy storage module to an external load according to the electric energy stored by the energy storage module.

16. The NFC interface with energy management function according to claim 15, wherein the rectifying module includes a diode rectifying bridge, a diode voltage drop of a diode in the diode rectifying bridge is less than 1V when an on current is 20mA, and/or the voltage stabilizing module includes a linear voltage stabilizer or a switching voltage stabilizer, and an output voltage range of the voltage stabilizing module is 1.7V to 3.6V.

17. The NFC interface with energy management function of claim 1, wherein the energy storage module comprises a storage capacitor.

18. The NFC interface with energy management function of claim 17, wherein a capacitance value of the storage capacitor is 22 μf to 0.47F.