CN105005753B - NFC communication device - Google Patents

Abstract

The invention discloses an NFC communication device, which includes a receiving link, a modulating link, a coil and a signal processing device; the receiving link receives a request signal sent by an external device through coil coupling, and demodulates the request signal and transmits it to the signal processing device Processing; the signal processing device controls the modulation link to couple with the coil of the external device through the coil, and sends a response signal corresponding to the request signal to the external device; the receiving link includes a Schmidt comparator, a level conversion device and a demodulator in series device; the other end of the Schmidt comparator is electrically connected to the first end of the coil; the modulation link includes a modulation device, a current conversion module and a current amplification device connected in series; the current conversion module is used to convert the voltage signal passed through the modulation device is a current signal; the current amplifying device is used to amplify the current signal; the other end of the current amplifying device is electrically connected to the coil. The above-mentioned NFC communication device has fewer electronic components and lower cost.

Description

NFC communication device

technical field

The invention relates to the technical field of near field communication, in particular to an NFC communication device.

Background technique

In recent years, with the development of the mobile Internet, mobile devices represented by smart phones have become more and more important information interaction terminals because of their portability, flexible and diverse application expansion, and other characteristics. The demand of mobile devices for short-distance interconnection technology makes the NFC (Near Field Communication, short-distance wireless communication) technology find a suitable application platform. Using NFC technology, you can easily and quickly realize identification, mobile payment, data exchange between two mobile devices, etc. The receiving link of a common NFC communication device is a circuit located outside the chip, and the receiving link located outside the chip requires many electronic components and high cost.

Contents of the invention

Based on this, it is necessary to provide an NFC communication device with fewer electronic components.

An NFC communication device, including a receiving link, a modulation link, a coil and a signal processing device; the receiving link receives a request signal sent by the external device through the coupling of the coil and the external device coil, and sends the The request signal is demodulated and transmitted to the signal processing device for processing; the signal processing device controls the modulation link to couple with the coil of the external device through the coil, and sends the signal corresponding to the request signal to the external device answer signal;

The receiving chain includes a Schmidt comparator, a level conversion device and a demodulation device connected in series; the other end of the Schmidt comparator is electrically connected to the first end of the coil;

The modulation link includes a modulation device, a current conversion module and a current amplification device connected in series in sequence; the current conversion module is used to convert the voltage signal passing through the modulation device into a current signal of a preset size; the current amplification device It is used to amplify the current signal; the other end of the current amplifying device is electrically connected to the coil.

In one of the embodiments, the receiving chain further includes an amplifying module, and the amplifying module includes a first switch and an amplifier group;

The first switch is connected in parallel with the amplifier group, the first end of the first switch is electrically connected to the first end of the coil, and the second end of the first switch is electrically connected to the Schmitt comparator connect;

The Schmitt comparator is electrically connected to the first end of the coil through the first switch or the amplifier group.

In one of the embodiments, the amplifier group includes one amplifier or more than two amplifiers connected in parallel, each of the amplifiers has a preset magnification range, and the magnification ranges of the amplifiers do not overlap

In one of the embodiments, the receiving link also receives the clock signal sent by the external device through the coil, and transmits the received clock signal to the signal processing device for processing;

When the modulation link is working and the modulation signal generated by the modulation link is at a high level, the amplitude of the clock signal becomes smaller, and in the load modulation mode, the signal processing device controls the amplifier group to work, so The amplifier group amplifies the amplitude of the portion where the amplitude of the clock signal becomes smaller to an amplitude value within a preset range.

In one of the embodiments, the receiving link further includes a first coupling capacitor, the first end of the first coupling capacitor is electrically connected to the first end of the first switch, and the first end of the first coupling capacitor The two ends are electrically connected to the first end of the coil;

The Schmitt comparator is electrically connected to the first end of the coil through the amplification module and the first coupling capacitor in turn.

In one of the embodiments, the receiving link further includes a current limiting resistor, the first end of the current limiting resistor is electrically connected to the first end of the first coupling capacitor, and the second end of the current limiting resistor electrically connected to the first end of the first switch;

The Schmitt comparator is electrically connected to the first end of the coil through the amplification module, the current limiting resistor and the first coupling capacitor in sequence.

In one of the embodiments, the receiving chain further includes a clamping circuit, and the Schmitt comparator is electrically connected to the first end of the coil through the clamping circuit and the amplification module in sequence.

In one of the embodiments, the clamping circuit includes a first resistor and a second resistor connected in series; the other end of the first resistor is connected to a power supply, and the other end of the second resistor is grounded; the first resistor The resistance value is equal to the resistance value of the second resistor.

In one of the embodiments, the current conversion module is a conversion resistor; or

The current conversion module is an adjustable current array, the power supply terminal of the adjustable current array is connected to the power supply, the controlled terminal of the adjustable current array is connected to the modulation device, and the output terminal of the adjustable current array is connected to the The current amplifying device.

In one of the embodiments, the current conversion module includes a second switch, a conversion resistor and an adjustable current array;

One end of the switching resistor is connected to the current amplification device, the other end of the switching resistor is connected to the output end of the adjustable current array and the first end of the second switch, the power supply terminal of the adjustable current array is connected to the power supply, The controlled terminal of the adjustable current array is connected to the modulation device, and the second terminal of the second switch is connected to the modulation device;

When the adjustable current array is working, the conversion resistance is short-circuited or the value of the conversion resistance is zero; when the adjustable current array is not working, the conversion resistance is a first resistance value.

In one of the embodiments, the current amplifying device is a triode, the base of the triode is electrically connected to the output terminal of the current conversion module, and the collector of the triode is electrically connected to the first end of the coil, The emitter of the triode is electrically connected with the second end of the coil.

In one of the embodiments, the NFC communication device further includes a second capacitor connected in parallel with the coil.

The above-mentioned NFC communication device, the receiving link includes a Schmitt comparator, a level conversion device and a demodulation device, and the modulation link includes a modulation device, a current conversion module and a current amplification device, and the pairing can be completed by using fewer electronic components. The demodulation and modulation of the request signal sent by the external device saves the cost. Further, the above-mentioned NFC communication device can also restore the clock signal sent by the external device to the reference clock signal of the modulation link, and the reference clock signal is recovered from the clock signal sent by the external device through the receiving link, so no additional Provides a reference clock with higher precision and smaller errors.

Description of drawings

Fig. 1 is the schematic diagram of the circuit structure of an embodiment of the NFC communication device of the present invention;

Fig. 2 is a schematic diagram of the waveforms of the request signal sent by the external device in an embodiment of the NFC communication device of the present invention passing through various places of the receiving link;

FIG. 3 is a schematic diagram of the waveforms of the clock signal sent by the external device in an embodiment of the NFC communication device of the present invention passing through various places of the receiving link under load modulation.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the specific implementation manner of the NFC communication device of the present invention will be described below with reference to the accompanying drawings. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Referring to FIG. 1 , in one embodiment, the NFC communication device of the present invention includes a receiving link 100 , a modulating link 200 , a coil L and a signal processing device 300 . The receiving link 100 receives the request signal sent by the external device through the coupling between the coil L and the coil of the external device, and demodulates the request signal and sends it to the signal processing device 300 . The signal processing device 300 controls the modulation link 200 to couple with the coil of the external device through the coil L, and sends a response letter corresponding to the request signal to the external device.

Specifically, the receiving chain 100 includes a Schmitt comparator 130 , a level conversion device 120 and a demodulation device 110 connected in series in sequence. One end of the Schmitt comparator 130 is electrically connected to the input end of the level conversion device 120 , and the other end is electrically connected to the first end of the coil L.

The modulation link 200 includes a modulation device 210 , a current conversion module 220 and a current amplification device 230 connected in series in sequence. The current converting module 220 is used for converting the modulated voltage signal passing through the modulating device 210 into a modulated current signal with a preset magnitude. The current amplifying device 230 is used for amplifying the modulated current signal. One end of the current amplifying device 230 is electrically connected to the output end of the current conversion module 220 , and the other end is electrically connected to the coil L.

It can be understood that when receiving a request signal sent by an external device, the modulation link 200 does not work, or the modulation strength is zero. At this time, the working condition of the receiving link 100 is as follows: the Schmidt comparator 130 processes the request signal received by the coil L into a high-low level digital signal; The digital signal is processed into a digital signal suitable for processing by the demodulation device 110; the demodulation device 110 demodulates the digital signal processed by the level conversion device 120 to obtain information sent by the external device.

After receiving the request signal sent by the external device, the signal processing device 300 controls the modulation link 200 to start working: the modulation device 210 outputs a modulation voltage signal according to the control of the signal processing device 300; the current conversion module 220 converts the modulation voltage signal sent by the modulation device 210 The signal is converted into a modulated current signal; the current amplifying device 230 amplifies the modulated current signal to generate modulation information, couples the coil L with the coil of the external device, and transmits the modulated information to the external device.

In the above-mentioned NFC communication device, the receiving link 100 includes a Schmitt comparator 130, a level conversion device 120 and a demodulation device 110, and the modulation link 200 includes a modulating device 210, a current conversion module 220 and a current amplifying device 230. Electronic components can complete the demodulation and modulation of the request signal sent by the external equipment, which saves the cost.

In this embodiment, the Schmitt comparator 130, the level conversion device 120 and the demodulation device 110 are all located in the chip of the NFC communication device, and the modulation device 210 and the current conversion module 220 are also located in the chip of the NFC communication device.

It can be understood that the amplitude of the signal sent by the external device received by the coil L is generally relatively large, so the signal sent by the external device can be directly passed to the Schmidt comparator 130 . However, when the amplitude of the signal sent by the external device received by the coil L is small, the signal needs to be amplified before being sent to the Schmidt comparator 130 . Therefore, the receive chain 100 may also include an amplification module 150 . Specifically, the amplifying module 150 includes a first switch S1 and an amplifier group 151 . Wherein, the first switch S1 is connected in parallel with the amplifier group 151 , the first end of the first switch S1 is electrically connected with the first end of the coil L, and the second end of the first switch S1 is electrically connected with the Schmitt comparator 130 . The Schmitt comparator 130 is electrically connected to the first end of the coil L through the first switch S1 or the amplifier group 150 .

In one embodiment, the amplifier group 151 includes two parallel amplifiers, such as a first amplifier O1 and a second amplifier O2. Both the first amplifier O1 and the second amplifier O2 have a preset amplification factor range, and the amplification factor ranges of the first amplifier O1 and the second amplifier O2 do not overlap. Preferably, the first amplifier O1 is a high-gain amplifier with a relatively large amplification factor, and the second amplifier O2 is a low-gain amplifier with a relatively small amplification factor. In this way, the first switch S1 , the first amplifier O1 and the second amplifier O2 form a structure with direct signal, low-gain amplification or high-gain amplification. Of course, both the first amplifier O1 and the second amplifier O2 can have several gears that can be adjusted, so that the structure formed by the first switch S1, the first amplifier O1 and the second amplifier O2 has a relatively high effect on the amplification gain or direct pass-through of the signal. Large adjustment range. Of course, in other embodiments, the amplifier group 151 may also include one amplifier or more than two amplifiers connected in parallel.

In an embodiment, the receiving chain 100 may further include a first coupling capacitor C1. The first coupling capacitor C1 is connected in series with the amplification module 150 . Specifically, the first end of the first coupling capacitor C1 is electrically connected to the first end of the first switch S1, and the second end of the first coupling capacitor C1 is electrically connected to the first end of the coil L. Therefore, the Schmitt comparator 130 is electrically connected to the first end of the coil L through the amplification module 150 and the first coupling capacitor C1 in sequence. The setting of the first coupling capacitor C1 can isolate the strong electric signal and the weak electric signal passing through the first coupling capacitor C1, and provide a path for high-frequency signals to prevent the power frequency current from entering the weak current system, so as to ensure the safe use of the equipment.

In one embodiment, it is considered that when the amplitude of the signal sent by the external device received by the coil L is too large, a relatively large current will flow into the receiving link 100, which may cause damage to various components of the receiving link 100 . Therefore, the receive chain 100 may also include a current limiting resistor R1. The current limiting resistor R1 is connected in series with the first coupling capacitor C1 and the amplification module 150 . The first terminal of the current limiting resistor R1 is electrically connected to the first terminal of the first coupling capacitor C1, and the second terminal of the current limiting resistor R1 is electrically connected to the first terminal of the first switch S1. The Schmitt comparator 130 is electrically connected to the first end of the coil L through the amplification module 150 , the current limiting resistor R1 and the first coupling capacitor C1 in sequence. The IO modules are well known to those skilled in the art, and for simplicity of description, the IO modules are not shown in the examples.

Preferably, the receiving chain 100 further includes a clamping circuit 140 . The Schmitt comparator 130 is electrically connected to the first end of the coil L through the clamping circuit 140 and the amplification module 150 in sequence. Specifically, the clamping circuit 140 may include a first resistor R2 and a second resistor R3 connected in series. The other end of the first resistor R2 is connected to the power supply, and the other end of the second resistor R3 is grounded. The resistance value of the first resistor R2 is equal to the resistance value of the second resistor R3. The clamping circuit 140 is provided, and the central value of the signal amplitude can be set to a half value of the power supply voltage of the clamping circuit 140 through the clamping circuit 140 . Certainly, the clamping circuit 140 may also have other circuit structures, and since the clamping circuit is a technology well known to those skilled in the art, details will not be repeated here.

In one embodiment, the current converting module 220 may be a converting resistor R4, and the two ends of the converting resistor R4 are electrically connected to the modulating device 210 and the current amplifying device 230 respectively. Under this solution, the modulation voltage signal sent by the modulation device 210 is converted into a modulation current signal after passing through the conversion resistor R4. The conversion resistor R4 can be a resistor with a fixed resistance, or a resistor with an adjustable resistance. The resistance value of the conversion resistor R4 can be any resistance value between tens of kiloohms to hundreds of kiloohms.

In addition, the current conversion module 220 can also be an adjustable current array 221 . The power supply terminal of the adjustable current array 221 is connected to the power supply, the controlled terminal of the adjustable current array 221 is connected to the modulation device 210 , and the output terminal of the adjustable current array 221 is connected to the current amplification device 230 . Under this scheme, the adjustable current array 221 is set to a suitable current value, and the modulated voltage signal sent by the modulation device 210 is converted into a modulated current signal after passing through the adjustable current array 221 .

In one embodiment, the current conversion module 220 may further include a second switch S2 , a conversion resistor R4 and an adjustable current array 221 . The modulation voltage signal sent by the modulation module 210 is converted into a modulation current signal through the conversion resistor R4 or the adjustable current array 221 . Specifically, the circuit structure of the current conversion module 220 may be: one end of the conversion resistor R4 is connected to the current amplifying device 230, and the other end of the conversion resistor R4 is connected to the output terminal of the adjustable current array 221 and the first terminal of the second switch S2. The power supply terminal of the adjustable current array 221 is connected to the power supply, the controlled terminal of the adjustable current array 221 is connected to the modulation device 210 , and the second terminal of the second switch S2 is connected to the modulation device 210 . When the adjustable current array 221 is working, the second switch S2 is turned on, and the switching resistor R4 is short-circuited or the resistance of the switching resistor R4 is zero. When the adjustable current array 221 is not working, the second switch S2 is closed, and the value of the switching resistor R4 is the first resistance value, which can be any resistance value between tens of kiloohms to hundreds of kiloohms. In this solution, the conversion resistor R4 can be a resistor with adjustable resistance.

It can be understood that, in other embodiments, the circuit structure of the current conversion module 220 may also be: the conversion resistor R4 is connected in series with the second switch S2, and the conversion resistor R4 and the second switch S2 connected in series are connected in parallel in the adjustable current array 221, Both ends of the series-connected switching resistor R4 and the second switch S2 are respectively electrically connected to the controlled end and the output end of the adjustable current array. At this time, the conversion resistor can be a resistor with a fixed resistance or a resistor with an adjustable resistance. The resistance value of the conversion resistor R4 can be any resistance value between tens of kiloohms to hundreds of kiloohms.

In one embodiment, the current amplifying device 230 is a triode Q. The output end of the current conversion module 220 is electrically connected to the base of the transistor Q. The collector of the triode Q is electrically connected to the first end of the coil L, and the emitter of the triode Q is electrically connected to the second end of the coil L. The transistor Q amplifies the modulated current signal to modulate the voltage amplitude in the coil L. Of course, in other embodiments, the current amplifying device 230 can also be other devices capable of amplifying current, and the cost of the transistor Q is relatively low.

It can be understood that, during the working process of the modulation link 200, the modulation link 200 needs a reference clock. While the modulation link 200 is working, the coil of the external device still sends a signal to the receiving link 100 through coupling with the coil L. Therefore, when the modulation link 200 is working, the signal sent by the external device can be restored to the reference clock required by the modulation link 200 through the receiving link 100, without additionally adding the reference clock signal required by the modulation link 200 .

Specifically, the receiving link 100 also receives the clock signal sent by the external device through the coil L, and sends the clock signal to the signal processing device 300 after processing. When the modulation link 200 is working and the modulation signal generated by the modulation link 200 is at a high level, the amplitude of the coupled clock signal will be pulled down under load modulation, and the signal processing device 300 will control the amplifier group 151 to work. The amplifier group 151 amplifies the amplitude of the portion where the amplitude of the clock signal becomes smaller to an amplitude value within a preset range. Specifically, the amplifier group 151 may amplify only the part of the pulled-down clock signal whose amplitude is pulled down, or may amplify the entirety of the pulled-down clock signal. Since the reference clock signal is recovered from the signal sent by the external device through the receiving link, there is no need to provide an additional reference clock, and the accuracy is higher and the error is smaller.

In this embodiment, the resistance value of the conversion resistor R4 cannot be too large or too small. If the resistance value of the conversion resistor R4 is too large, the modulation depth of the modulation link 200 is too small, and the modulation link 200 may not be able to play a modulation role; If the resistance of the conversion resistor R4 is too small, the modulation depth of the modulation link 200 is too large, which may affect the recovery of the reference clock. Specifically, the resistance value of the conversion resistor R4 can be selected between tens of kiloohms to hundreds of kiloohms. Certainly, the resistance value of the conversion resistor R4 is also related to the amplification factor of the transistor Q and the amplification factor of the amplifier group 151 . Therefore, the value range of the above-mentioned resistance value of the conversion resistor R4 is only a suggested value, and the specific value can be changed according to the actual application situation.

In this embodiment, the parts other than the first coupling capacitor C1 and the current limiting resistor R1 in the receiving link 100 can all be located in the chip of the NFC communication device, and the parts other than the current amplifying device 230 and the conversion resistor R4 in the modulation link 200 Both may be located in the chip of the NFC communication device.

In one embodiment, the NFC communication device further includes a second capacitor C2 connected in parallel with the coil L. By selecting the appropriate coil model, that is, the size of the inductance value, and the size of the appropriate second capacitance value, the resonance point can be adjusted to near the operating frequency of NFC (for example, 13.56MHz), so it has better frequency selection characteristics. The coupling effect between L and the coil of the external device is better, and the signal transmission is better.

Referring to FIG. 1 , FIG. 2 and FIG. 3 , the structure and working process of the NFC communication device of the present invention will be further described.

Referring to FIG. 1 , the receiving chain 100 includes a first coupling capacitor C1 , a current limiting resistor R1 , an amplifying module 150 , a clamping circuit 140 , a Schmitt comparator 130 , a level shifting device 120 and a demodulating device 110 in series. Wherein, the amplifying module 150 includes a first switch S1, a first amplifier O1 and a second amplifier O2 connected in parallel. The clamping circuit 140 includes two first resistors R2 and second resistors R3 connected in series. The level shifting device 120 may be a level shifter. The demodulation device 110 may be a demodulator. A first end of the first coupling capacitor C1 is electrically connected to the current limiting resistor R1.

The modulation link 200 includes a triode Q, a current amplification device 220 and a modulation device 210 connected in series in sequence. Wherein, the current amplifying device 220 includes a conversion resistor R4 , a second switch S2 and an adjustable current array 221 . One end of the conversion resistor R4 is connected to the current amplifying device 230 , and the other end of the conversion resistor R4 is connected to the output end of the adjustable current array 221 and the first end of the second switch S2 . The power supply terminal of the adjustable current array 221 is connected to the power supply, the controlled terminal of the adjustable current array 221 is connected to the modulation device 210 , and the second terminal of the second switch S2 is connected to the modulation device 210 .

Two ends of the coil L are connected in parallel with a second capacitor C2. The first end of the coil L is electrically connected to the other end of the first coupling capacitor C1 and the collector of the transistor Q, the second end of the coil L is electrically connected to the emitter of the transistor Q, and the second end of the coil L is grounded. The other end of the demodulation device 110 is electrically connected to the signal processing device 300 . The other end of the modulation device 210 is electrically connected to the signal processing device 300 . According to the non-contact specification, different types of interface communication signals are different. In this embodiment, the ASK (Amplitude Shift Keying, amplitude keying) 100% modulation of Class A is used as an example to illustrate the functions and functions of the NFC communication device of the present invention. Advantage. In the class A ASK100% modulation process, the communication between PCD (proximity coupling device) and PICC (proximity card) is carried out through the "pause" state. The "pause" state can be understood as the monotonous envelope of the PCD field The portion of the interval that decrements to less than 5% of its initial value.

Referring to Figure 2, the PICC is placed in the RF field of the PCD reader-writer. At this time, the coil of the PCD reader-writer is close to the coil L, and the waveform of the request signal sent by the PCD reader-writer is shown in A1 waveform in Figure 2. The coil L transmits the request signal received from the PCD reader to the receiving link 100. After passing through the first coupling capacitor C1, the current limiting resistor R1 and the first switch S1, the formed signal is shown in the B1 waveform. Since the first switch S1 of the amplifying module 150 works, but the amplifier group 151 does not work, the amplitude of the B1 waveform does not change relative to the amplitude of the A1 waveform. Of course, if the amplifier group 151 is selected to work but the first switch S1 is not working, the amplitude of the B1 waveform will change relative to the amplitude of the A1 waveform. The B1 waveform signal passes through the clamping circuit 140. Since the clamping circuit 140 includes two first resistors R2 and second resistors R3 with equal resistance, the value of the central point of the B1 waveform amplitude is the clamping circuit 140 power supply voltage V _DD value half of. The Schmitt comparator 130 can set the signal higher than the preset threshold voltage to a high level, and the signal lower than the preset threshold voltage to be set to a low level, so the B1 waveform signal passes through the clamping circuit 140 and Schmitt After the comparator 130, the formed signal is shown as C1 waveform. Since the working voltage of the demodulation device 110 is 1.2V, and the high level of the C1 waveform signal is 3.3V, the high level of the C1 waveform signal needs to be converted to 1.2V by using the level conversion device 120 . The demodulation device 110 demodulates the signal whose level has been converted by the level conversion device 120 , and sends it to the signal processing device 300 .

The modulation device 210 outputs the modulation signal CLKm according to the control of the signal processing device 300 . At this time, the modulation signal CLKm is a modulation voltage signal. The modulation signal CLKm can be modulated in the following two ways. One way is to turn off the adjustable current array 221, close the second switch S2, and convert the modulation voltage signal CLKm into a modulation current signal through the second switch S2 and the conversion resistor R4. At this time, the conversion resistor R4 has a certain resistance value. Another way is to turn off the second switch S2, adjust the conversion resistance R4 to zero resistance or short-circuit the conversion resistance R4, and set the adjustable current array 221 to an appropriate current value, and adjust the modulation current through the adjustable current array 221 The voltage signal CLKm is converted into a modulated current signal. Then the modulated current signal is amplified by the transistor Q.

After receiving the signal sent by the PCD reader-writer, the PICC needs to reply the response signal, and when the PICC does not output the modulation signal, the PCD reader-writer will continue to send the 13.56MHz clock signal, which can be transmitted after receiving the link 100 Used as a reference clock for the modulation link 200. Referring to Figure 3, when the modulating signal CLKm is at a high level, the amplitude of the 13.56MHz clock signal sent by the PCD reader-writer received by the coil L will be pulled down, and the clock signal after being pulled down is shown in A2, and is pulled down The low clock signal A2 is inaccurate as the reference clock of the modulation link 200 . In this embodiment, after the signal processing device 300 detects the pulled-down clock signal A2, it controls the amplifier group 151 to work, and amplifies the pulled-down part of the pulled-down clock signal A2 to the preset range. value, as shown in B2. After the signal B2 passes through the clamping circuit 140 and the Schmitt comparator 130, the generated signal is shown as C2. The signal C2 meets the requirements of the reference clock signal of the modulation link 200 and can be used as the reference clock signal of the modulation link 200 .

It should be noted that the signal processing device 300 can control the amplifier group 151 to work with an appropriate gain, and amplify the lowered part of the pulled-down clock signal A2 to a preset range of amplitude values. However, there is no requirement for the portion of the amplitude of the pulled-down clock signal A2 that is not pulled down. That is, the amplifier group 151 may amplify only the part of the pulled-down clock signal A2 whose amplitude is pulled down, or may amplify the entire pulled-down clock signal A2.

The above-mentioned NFC communication device can complete the demodulation and modulation of the request signal sent by the external device by using fewer electronic components, thereby saving costs. In addition, the receiving link 100 can also restore the clock signal sent by the external device when the modulating link 200 is working, and finally generate the reference clock signal of the modulating link 200, so that there is no need to add additional components required by the modulating link 200. A reference clock signal, and since the reference clock signal is recovered from the signal sent by the external device through the receiving link 100, there is no need to provide an additional reference clock, and the accuracy is high and the error is small.

The above-mentioned embodiments only express several implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but should not be construed as limiting the patent scope of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (12)

1. A kind of NFC communication device, is characterized in that, comprises receiving link, modulating link, coil and signal processing device; Described receiving link receives the request that described external equipment sends by the coupling of described coil and external equipment coil signal, and demodulates the request signal and transmits it to the signal processing device for processing; the signal processing device controls the modulation link to couple with the coil of the external device through the coil, to the external device sending a response signal corresponding to the request signal; The receiving chain includes a Schmidt comparator, a level conversion device and a demodulation device connected in series; the other end of the Schmidt comparator is electrically connected to the first end of the coil; The modulation link includes a modulation device, a current conversion module and a current amplification device connected in series in sequence; the current conversion module is used to convert the modulation voltage signal passing through the modulation device into a modulation current signal of a preset size; the current The amplifying device is used to amplify the current signal; the other end of the current amplifying device is electrically connected to the coil. 2. The NFC communication device according to claim 1, wherein the receiving link further comprises an amplifying module, and the amplifying module comprises a first switch and an amplifier group; The first switch is connected in parallel with the amplifier group, the first end of the first switch is electrically connected to the first end of the coil, and the second end of the first switch is electrically connected to the Schmitt comparator connect; The Schmitt comparator is electrically connected to the first end of the coil through the first switch or the amplifier group. 3. The NFC communication device according to claim 2, wherein the amplifier group comprises one amplifier or more than two amplifiers connected in parallel, each of the amplifiers has a preset magnification range, and each of the amplifiers The magnification ranges of the above mentioned amplifiers do not overlap. 4. The NFC communication device according to claim 2, wherein the receiving link also receives the clock signal sent by the external device through the coil, and transmits the clock signal to the signal after processing the clock signal processing device; When the modulation link is working and the modulation signal generated by the modulation link is at a high level, the amplitude of the clock signal becomes smaller, and in the load modulation mode, the signal processing device controls the amplifier group to work, so The amplifier group amplifies the amplitude of the portion where the amplitude of the clock signal becomes smaller to an amplitude value within a preset range. 5. The NFC communication device according to claim 2, wherein the receiving link further comprises a first coupling capacitor, the first end of the first coupling capacitor is electrically connected to the first end of the first switch. connected, the second end of the first coupling capacitor is electrically connected to the first end of the coil; The Schmitt comparator is electrically connected to the first end of the coil through the amplification module and the first coupling capacitor in turn. 6. The NFC communication device according to claim 5, wherein the receiving link further comprises a current limiting resistor, the first end of the current limiting resistor is electrically connected to the first end of the first coupling capacitor , the second end of the current limiting resistor is electrically connected to the first end of the first switch; The Schmitt comparator is electrically connected to the first end of the coil through the amplification module, the current limiting resistor and the first coupling capacitor in sequence. 7. The NFC communication device according to claim 2, wherein the receiving link further comprises a clamping circuit, and the Schmidt comparator communicates with the clamping circuit and the amplifying module successively through the clamping circuit and the The first ends of the coils are electrically connected. 8. The NFC communication device according to claim 7, wherein the clamping circuit includes a first resistor and a second resistor connected in series; the other end of the first resistor is connected to a power supply, and the second resistor The other end of the resistor is grounded; the resistance value of the first resistor is equal to the resistance value of the second resistor. 9. The NFC communication device according to claim 1, wherein the current conversion module is a conversion resistor; or The current conversion module is an adjustable current array, the power supply terminal of the adjustable current array is connected to the power supply, the controlled terminal of the adjustable current array is connected to the modulation device, and the output terminal of the adjustable current array is connected to the The current amplifying device. 10. The NFC communication device according to claim 1, wherein the current conversion module comprises a second switch, a conversion resistor and an adjustable current array; One end of the switching resistor is connected to the current amplifying device, the other end of the switching resistor is connected to the output end of the adjustable current array and the first end of the second switch, and the power supply terminal of the adjustable current array is connected to A power supply, the controlled terminal of the adjustable current array is connected to the modulation device, and the second terminal of the second switch is connected to the modulation device; When the adjustable current array is working, the conversion resistance is short-circuited or the value of the conversion resistance is zero; when the adjustable current array is not working, the conversion resistance is a first resistance value. 11. The NFC communication device according to claim 1, wherein the current amplifying device is a triode, the base of the triode is electrically connected to the output terminal of the current conversion module, and the collector of the triode is connected to the output terminal of the current conversion module. The first end of the coil is electrically connected, and the emitter of the triode is electrically connected with the second end of the coil. 12. The NFC communication device according to any one of claims 1 to 11, characterized in that the NFC communication device further comprises a second capacitor connected in parallel with the coil.