阅读说明：本技术 一种用于智能阀门定位器的本安hart通讯系统 (Intrinsic safety HART communication system for intelligent valve positioner ) 是由 薛斌 胡孟杰 沈一鹏 黄兴 于 2021-08-23 设计创作，主要内容包括：本发明公开了一种用于智能阀门定位器的本安HART通讯系统,包括：用于接收外部输入HART信号的本安输入输出模块,起到保护电路以及对接收的HART通讯信号实现滤波和EMC抑制。用于从本安输入输出模块接收HART信号并分成两路输出的HART输入隔离模块,一路为供电电源为本安HART通讯系统提供电力支持,另一路为分离HART信号。用于接收分离HART信号进行解调的HART调制解调模块。用于接收解调后的分离HART信号进行信号处理的CPU模块,并得到反馈信号送入HART调制解调模块进行调制。用于接收调制后的反馈信号耦合至HART信号后经本安输入输出模块输出至外部的HART输出耦合模块。本发明中的HART信号传输损耗低、抗干扰性强、满足本安要求、信号幅度可调节。(The invention discloses an intrinsic safety HART communication system for an intelligent valve positioner, which comprises: the intrinsic safety input and output module is used for receiving external input HART signals, and plays a role in protecting a circuit and realizing filtering and EMC inhibition on the received HART communication signals. And the HART input isolation module is used for receiving HART signals from the intrinsic safety input/output module and dividing the HART signals into two paths for output, one path provides power support for the intrinsic safety HART communication system for the power supply, and the other path is used for separating HART signals. And the HART modulation and demodulation module is used for receiving the separated HART signals and demodulating the separated HART signals. And the CPU module is used for receiving the demodulated separated HART signal to perform signal processing, and obtaining a feedback signal and sending the feedback signal to the HART modulation and demodulation module for modulation. And the HART output coupling module is used for receiving the modulated feedback signal, coupling the modulated feedback signal to the HART signal and outputting the HART signal to the outside through the intrinsic safety input output module. The HART signal transmission loss is low, the anti-interference performance is strong, the intrinsic safety requirement is met, and the signal amplitude is adjustable.)

1. An intrinsically safe HART communication system for a smart valve positioner, comprising: the system comprises an intrinsic safety input/output module, an HART input isolation module, an HART modulation/demodulation module, a CPU module and an HART output coupling module;

the intrinsic safety input/output module is used for receiving externally input HART signals, protecting a circuit and realizing filtering and EMC inhibition on the received HART communication signals;

the HART input isolation module is used for receiving the HART signal from the intrinsic safety input/output module and dividing the HART signal into two paths for output, one path is a power supply and is used for providing power support for the intrinsic safety HART communication system, and the other path is a separated HART signal;

the HART modulation and demodulation module is used for receiving the separated HART signal and demodulating the separated HART signal;

the CPU module is used for receiving the demodulated separated HART signal to perform signal processing, and obtaining a feedback signal to be sent to the HART modulation and demodulation module to be modulated;

and the HART output coupling module is used for receiving the modulated feedback signal, coupling the modulated feedback signal to the HART signal and outputting the HART signal to the outside through the intrinsic safety input output module.

2. The intrinsically safe HART communication system for a smart valve positioner of claim 1, wherein the intrinsically safe input output module comprises a protection circuit and a filtered EMC suppression circuit, one end of the protection circuit is electrically connected to the outside, the other end of the protection circuit is electrically connected to one end of the filtered EMC suppression circuit, and the other end of the filtered EMC suppression circuit is electrically connected to the HART input isolation module and the HART output coupling module, respectively.

3. The intrinsically-safe HART communication system of claim 2, wherein the protection circuit comprises a TVS tube, a first diode, a second diode, a third diode, a fourth diode, a fifth diode, and a fuse;

one end of the TVS tube is electrically connected with the anode of the first diode, the cathode of the first diode is electrically connected with the anode of the second diode, the cathode of the second diode is electrically connected with the anode of the third diode, the cathode of the third diode is electrically connected with one end of the fuse, the other end of the fuse is electrically connected with the cathode of the fourth diode and the cathode of the fifth diode respectively, and the other end of the TVS tube is electrically connected with the anode of the fourth diode and the anode of the fifth diode respectively.

4. The intrinsically safe HART communication system for a smart valve positioner of claim 3, wherein the filtered EMC suppression circuit comprises a first BL, a second BL, a connector, a first capacitance, a first resistance, a first inductance, and a second inductance;

one end of the first BL is electrically connected to the other end of the fuse, the negative electrode of the fourth diode, and the negative electrode of the fifth diode, respectively, the other end of the first BL is electrically connected to the first connection port of the connector, one end of the second BL is electrically connected to the other end of the TVS tube, the positive electrode of the fourth diode, and the positive electrode of the fifth diode, respectively, the other end of the second BL is electrically connected to the second connection port of the connector, the second port of the connector is electrically connected to one end of the first capacitor and one end of the first inductor, respectively, the other end of the first inductor is electrically connected to the HART input isolation module, the other end of the first capacitor is electrically connected to one end of the first resistor, and the other end of the first resistor is electrically connected to the third connection port of the connector and one end of the second inductor, respectively, the other end of the second inductor is electrically connected with the output end of the HART output coupling module.

5. The intrinsically-safe HART communication system for a smart valve positioner as claimed in claim 1, wherein the HART input isolation module comprises a second resistor and a DC-DC converter, one end of the second resistor is electrically connected to the intrinsically-safe input/output module and the HART modem module respectively, and the other end of the second resistor outputs a 3V power supply after passing through the DC-DC converter.

6. The intrinsically-safe HART communication system for a smart valve positioner of claim 1, wherein the HART modem module comprises an intrinsically-safe energy limiting circuit, a signal filtering circuit, and a HART modem; the input end of the intrinsic safety energy limiting circuit is electrically connected with the output end of the HART input isolation module, the input end of the signal filtering circuit is electrically connected with the output end of the intrinsic safety energy limiting circuit, and the output end of the signal filtering circuit is electrically connected with the input end of the HART modem.

7. The intrinsically safe HART communication system for a smart valve positioner of claim 6,

the intrinsic safety energy limiting circuit comprises a third resistor, a second capacitor, a first voltage regulator tube and a second voltage regulator tube, wherein one end of the third resistor is an input end of the intrinsic safety energy limiting circuit, the other end of the third resistor is electrically connected with one end of the second capacitor, the other end of the second capacitor is an output end of the intrinsic safety energy limiting circuit and is respectively and electrically connected with the negative electrodes of the first voltage regulator tube and the second voltage regulator tube, and the positive electrodes of the first voltage regulator tube and the second voltage regulator tube are grounded;

the signal filter circuit comprises a fourth resistor, a third capacitor and a fourth capacitor, one end of the fourth resistor is an input end of the signal filter circuit, the other end of the fourth resistor is respectively electrically connected with one end of the third capacitor and one end of the fourth capacitor, the other end of the third capacitor is an output end of the signal filter circuit, and the other end of the fourth capacitor is grounded.

8. The intrinsically-safe HART communication system for a smart valve positioner of claim 7, further comprising a first amplification circuit disposed between the third resistor and the second capacitor, the first amplification circuit comprising a fifth capacitor, a sixth capacitor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, and a first operational amplifier;

one end of the fifth capacitor is connected with the third resistor, the other end of the fifth capacitor is respectively electrically connected with one end of the fifth resistor, one end of the sixth resistor and the non-inverting input end of the first operational amplifier, the other end of the fifth resistor is respectively electrically connected with one end of the sixth capacitor and the positive power source end of the first operational amplifier, the other end of the sixth capacitor is grounded, the other end of the sixth resistor is grounded, the inverting input end of the first operational amplifier is respectively electrically connected with one end of the seventh resistor and one end of the eighth resistor, the other end of the seventh resistor is grounded, the other end of the eighth resistor is respectively electrically connected with the output end of the first operational amplifier and one end of the ninth resistor, and the other end of the ninth resistor is electrically connected with the second capacitor.

9. The intrinsically-safe HART communication system for a smart valve positioner of claim 2, wherein the HART output coupling module comprises a current-limiting isolation circuit and a coupling circuit;

the input end of the current-limiting isolation circuit is electrically connected with the output end of the HART modulation and demodulation module, the output end of the current-limiting isolation circuit is electrically connected with the input end of the coupling circuit, and the output end of the coupling circuit is electrically connected with the input end of the filtering EMC suppression circuit;

the current-limiting isolation circuit comprises a seventh capacitor and a tenth resistor, one end of the seventh capacitor is an input end of the current-limiting isolation circuit, the other end of the seventh capacitor is electrically connected with one end of the tenth resistor, and the other end of the tenth resistor is an output end of the current-limiting isolation circuit;

the coupling circuit comprises an eleventh resistor, a twelfth resistor, a thirteenth resistor, a third voltage-regulator tube, a fourth voltage-regulator tube and a field-effect tube, wherein the input end of the coupling circuit is electrically connected with one end of the eleventh resistor, one end of the twelfth resistor, the negative electrode of the third voltage-regulator tube, the negative electrode of the fourth voltage-regulator tube and the grid electrode of the field-effect tube respectively, the other end of the eleventh resistor, the positive electrode of the third voltage-regulator tube and the positive electrode of the fourth voltage-regulator tube are all grounded, the other end of the twelfth resistor is electrically connected with a power supply, the drain electrode of the field-effect tube is electrically connected with one end of the thirteenth resistor, the other end of the thirteenth resistor is grounded, and the source electrode of the field-effect tube is the output end of the coupling circuit.

10. The intrinsically safe HART communication system of claim 9, wherein a second amplifying circuit is further disposed between the seventh resistor and the tenth resistor, the second amplifying circuit comprises a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, an eighth capacitor and a second operational amplifier, the other end of the seventh capacitor is electrically connected to one end of the fourteenth resistor, one end of the fifteenth resistor and the non-inverting input terminal of the second operational amplifier, the other end of the fourteenth resistor is connected to a power supply, the other end of the fifteenth resistor is grounded, the inverting input terminal of the second operational amplifier is electrically connected to one end of the sixteenth resistor and one end of the seventeenth resistor, the other end of the sixteenth resistor is grounded, the other end of the seventeenth resistor is electrically connected to the output terminal of the second operational amplifier and one end of the eighth capacitor, the other end of the eighth capacitor is electrically connected with one end of the tenth resistor.

Technical Field

The invention belongs to the technical field of intelligent valve positioners, and particularly relates to an intrinsic safety HART communication system for an intelligent valve positioner.

Background

At present, most intelligent valve positioners adopt a transformer isolation coupling or inductance coil isolation coupling mode to isolate and couple HART signals, communication receiving and transmitting are not separated, so that the intelligent valve positioners have the defects of high communication signal loss, large distortion, low anti-interference performance and the like when carrying out HART communication, and particularly, under the condition that a circuit simultaneously meets the intrinsic safety requirement, the circuit performance is reduced to some extent, and the HART communication quality is influenced. In the prior art, the transformer isolation coupling or the inductance coil isolation coupling mode is adopted to isolate and couple the HART signal, the transmission loss of the HART carrier signal is large, the distortion is easy, and the intrinsic safety explosion-proof requirement cannot be met. Resulting in poor isolation coupling effect of the transformer and the inductor. In addition, the HART communication signal receiving and transmitting link is not separated, the HART signal anti-interference performance is low, the transmitted signal loss is large, the fidelity is easy, the HART communication of the intelligent valve positioner is influenced, and the separation effect of the communication signal receiving and transmitting link is poor. In addition, if the circuit does not match after increasing the design of this ampere of explosion-proof device, signal transmission loss can grow, and the circuit performance descends to some extent, can influence HART communication quality, and it is poor to satisfy this ampere of effect after requiring.

Disclosure of Invention

The invention aims to provide an intrinsic safety HART communication system for an intelligent valve positioner, and aims to solve the technical problems of high communication signal loss, high distortion, low anti-interference performance and incapability of meeting intrinsic safety explosion-proof requirements in HART communication.

In order to solve the problems, the technical scheme of the invention is as follows:

an intrinsically safe HART communication system for a smart valve positioner, comprising: the system comprises an intrinsic safety input/output module, a HART input isolation module, a HART modulation/demodulation module, a CPU module and a HART output coupling module. The intrinsic safety input and output module is used for receiving externally input HART signals, protecting the circuit and filtering and EMC inhibiting the received HART communication signals. And the HART input isolation module is used for receiving HART signals from the intrinsic safety input output module and dividing the HART signals into two paths of output, one path is a power supply and is used for providing power support for the intrinsic safety HART communication system, and the other path is separated HART signals. And the HART modulation and demodulation module is used for receiving the separated HART signals and demodulating the separated HART signals. And the CPU module is used for receiving the demodulated separated HART signal to perform signal processing, and obtaining a feedback signal and sending the feedback signal to the HART modulation and demodulation module for modulation. And the HART output coupling module is used for receiving the modulated feedback signal, coupling the modulated feedback signal to a HART signal and outputting the HART signal to the outside through the intrinsic safety input output module.

Specifically, this ampere of input/output module includes protection circuit and filtering EMC suppression circuit, and protection circuit's one end is connected with the outside electricity, and protection circuit's the other end is connected with filtering EMC suppression circuit's one end electricity, and filtering EMC suppression circuit's the other end is connected with HART input isolation module and HART output coupling module electricity respectively.

Specifically, the protection circuit comprises a TVS tube, a first diode, a second diode, a third diode, a fourth diode, a fifth diode and a fuse.

One end of the TVS tube is electrically connected with the anode of the first diode, the cathode of the first diode is electrically connected with the anode of the second diode, the cathode of the second diode is electrically connected with the anode of the third diode, the cathode of the third diode is electrically connected with one end of the fuse, the other end of the fuse is electrically connected with the cathode of the fourth diode and the cathode of the fifth diode respectively, and the other end of the TVS tube is electrically connected with the anode of the fourth diode and the anode of the fifth diode respectively.

Specifically, the filtering EMC suppression circuit includes a first BL, a second BL, a connector, a first capacitance, a first resistance, a first inductance, and a second inductance.

One end of the first BL is electrically connected with the other end of the fuse, the cathode of the fourth diode and the cathode of the fifth diode respectively, the other end of the first BL is electrically connected with the first connection port of the connector, one end of the second BL is electrically connected with the other end of the TVS tube, the anode of the fourth diode and the anode of the fifth diode respectively, the other end of the second BL is electrically connected with the second connection port of the connector, the second port of the connector is electrically connected with one end of the first capacitor and one end of the first inductor respectively, the other end of the first inductor is electrically connected with the HART input isolation module, the other end of the first capacitor is electrically connected with one end of the first resistor, the other end of the first resistor is electrically connected with the third connection port of the connector and one end of the second inductor respectively, and the other end of the second inductor is electrically connected with the output end of the HART output coupling module.

Specifically, the HART input isolation module comprises a second resistor and a DC-DC converter, one end of the second resistor is electrically connected with the intrinsically safe input/output module and the HART modem module, and the other end of the second resistor outputs a 3V power supply after passing through the DC-DC converter.

Specifically, the HART modem module comprises an intrinsic safety energy limiting circuit, a signal filtering circuit and a HART modem. The input end of the intrinsic safety energy limiting circuit is electrically connected with the output end of the HART input isolation module, the input end of the signal filtering circuit is electrically connected with the output end of the intrinsic safety energy limiting circuit, and the output end of the signal filtering circuit is electrically connected with the input end of the HART modem.

Specifically, the intrinsic safety energy limiting circuit comprises a third resistor, a second capacitor, a first voltage regulator tube and a second voltage regulator tube, one end of the third resistor is an input end of the intrinsic safety energy limiting circuit, the other end of the third resistor is electrically connected with one end of the second capacitor, the other end of the second capacitor is an output end of the intrinsic safety energy limiting circuit and is respectively electrically connected with negative electrodes of the first voltage regulator tube and the second voltage regulator tube, and positive electrodes of the first voltage regulator tube and the second voltage regulator tube are both grounded.

The signal filter circuit comprises a fourth resistor, a third capacitor and a fourth capacitor, one end of the fourth resistor is an input end of the signal filter circuit, the other end of the fourth resistor is electrically connected with one end of the third capacitor and one end of the fourth capacitor respectively, the other end of the third capacitor is an output end of the signal filter circuit, and the other end of the fourth capacitor is grounded.

Further preferably, the circuit further comprises a first amplifying circuit, the first amplifying circuit is arranged between the third resistor and the second capacitor, and the first amplifying circuit comprises a fifth capacitor, a sixth capacitor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor and a first operational amplifier.

One end of a fifth capacitor is connected with the third resistor, the other end of the fifth capacitor is respectively electrically connected with one end of the fifth resistor, one end of a sixth resistor and the non-inverting input end of the first operational amplifier, the other end of the fifth resistor is respectively electrically connected with one end of the sixth capacitor and the positive power source end of the first operational amplifier, the other end of the sixth capacitor is grounded, the other end of the sixth resistor is grounded, the inverting input end of the first operational amplifier is respectively electrically connected with one end of a seventh resistor and one end of an eighth resistor, the other end of the seventh resistor is grounded, the other end of the eighth resistor is respectively electrically connected with the output end of the first operational amplifier and one end of a ninth resistor, and the other end of the ninth resistor is electrically connected with the second capacitor.

Specifically, the HART output coupling module includes a current limiting isolation circuit and a coupling circuit.

The input end of the current-limiting isolation circuit is electrically connected with the output end of the HART modulation and demodulation module, the output end of the current-limiting isolation circuit is electrically connected with the input end of the coupling circuit, and the output end of the coupling circuit is electrically connected with the input end of the filtering EMC suppression circuit.

The current-limiting isolation circuit comprises a seventh capacitor and a tenth resistor, one end of the seventh capacitor is an input end of the current-limiting isolation circuit, the other end of the seventh capacitor is electrically connected with one end of the tenth resistor, and the other end of the tenth resistor is an output end of the current-limiting isolation circuit.

The coupling circuit comprises an eleventh resistor, a twelfth resistor, a thirteenth resistor, a third voltage-regulator tube, a fourth voltage-regulator tube and a field-effect tube, wherein the input end of the coupling circuit is respectively electrically connected with one end of the eleventh resistor, one end of the twelfth resistor, the negative electrode of the third voltage-regulator tube, the negative electrode of the fourth voltage-regulator tube and the grid electrode of the field-effect tube, the other end of the eleventh resistor, the positive electrode of the third voltage-regulator tube and the positive electrode of the fourth voltage-regulator tube are all grounded, the other end of the twelfth resistor is electrically connected with a power supply, the drain electrode of the field-effect tube is electrically connected with one end of the thirteenth resistor, the other end of the thirteenth resistor is grounded, and the source electrode of the field-effect tube is the output end of the coupling circuit.

Further preferably, a second amplifying circuit is further disposed between the seventh capacitor and the tenth resistor, the second amplifying circuit includes a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, an eighth capacitor and a second operational amplifier, the other end of the seventh capacitor is electrically connected to one end of the fourteenth resistor, one end of the fifteenth resistor and a non-inverting input terminal of the second operational amplifier, the other end of the fourteenth resistor is connected to the power supply, the other end of the fifteenth resistor is grounded, an inverting input terminal of the second operational amplifier is electrically connected to one end of the sixteenth resistor and one end of the seventeenth resistor, the other end of the sixteenth resistor is grounded, the other end of the seventeenth resistor is electrically connected to an output terminal of the second operational amplifier and one end of the eighth capacitor, and the other end of the eighth capacitor is electrically connected to one end of the tenth resistor.

Due to the adoption of the technical scheme, compared with the prior art, the invention has the following advantages and positive effects:

(1) the invention realizes that the coupling circuit of the field effect tube is used for replacing the transformer coupling circuit adopted by the existing intelligent valve positioner, thereby reducing the loss in HART signal transmission;

(2) the invention realizes the separation of HART communication receiving and transmitting, has strong anti-interference performance of HART signals and high fidelity of HART signals, and ensures the high-quality communication of the HART signals of the intelligent valve positioner;

(3) the invention adopts various intrinsic safety explosion-proof device designs and matching circuits to replace the HART circuit of the traditional intelligent valve positioner, and can meet the requirement that the HART communication is carried out on the intelligent valve positioner in an explosive environment;

(4) the preset amplifying circuit can amplify signals and has an isolating function, and can meet the requirement of ultra-long-distance HART communication of the intelligent valve positioner.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention.

FIG. 1 is a schematic block diagram of an intrinsically safe HART communication system for a smart valve positioner of the present invention;

FIG. 2 is a circuit diagram of the intrinsically safe I/O module and the HART input isolation module of the present invention;

FIG. 3 is a schematic circuit diagram of a HART modem module, a CPU module and a HART output coupling module according to the present invention;

FIG. 4 is a circuit diagram of a first amplifying circuit according to the present invention;

fig. 5 is a circuit diagram of a second amplifying circuit according to the present invention.

Description of reference numerals:

10: the intrinsic safety input and output module; 20: an HART input isolation module; 30: a CPU module; 40: HART modulation-demodulation module; 50: HART output coupling module.

Detailed Description

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following description will be made with reference to the accompanying drawings. It is obvious that the drawings in the following description are only some examples of the invention, and that for a person skilled in the art, other drawings and embodiments can be derived from them without inventive effort.

For the sake of simplicity, the drawings only schematically show the parts relevant to the present invention, and they do not represent the actual structure as a product. In addition, in order to make the drawings concise and understandable, components having the same structure or function in some of the drawings are only schematically illustrated or only labeled. In this document, "one" means not only "only one" but also a case of "more than one".

The HART communication system for intelligent valve positioner according to the present invention will be described in detail with reference to the accompanying drawings and embodiments. Advantages and features of the present invention will become apparent from the following description and from the claims.

Examples

Referring to fig. 1, the embodiment provides an intrinsically safe HART communication system for an intelligent valve positioner, which is composed of an intrinsically safe input/output module 10, a HART input isolation module 20, a HART modem module 40, a CPU module 30, and a HART output coupling module 50. In the embodiment, the high-quality HART modulation and demodulation chip, HART communication transceiving separation, the field effect tube, various intrinsic safety explosion-proof matching devices and other design modes are adopted, so that the problems of high signal loss, large distortion, low anti-interference performance, incapability of meeting intrinsic safety explosion-proof requirements and the like in the HART communication of the existing intelligent valve positioner are solved.

In the present embodiment, the external signal of the HART communicator is superimposed on the HART signal of 4mA to 20mA and then input through the intrinsically safe input/output module 10, and the intrinsically safe input/output module 10 receives the HART signal to protect the subsequent circuit, and further performs filtering and EMC suppression on the received HART signal. The superimposed HART signal is input to the HART input isolation module 20 and then split into two paths for output, wherein one path is used as a power supply for providing power support for the embodiment, and the other path outputs the split HART signal. The separated HART signal is input to the HART modulation and demodulation module 40, and the HART modulation and demodulation module 40 demodulates the separated HART signal. The CPU module 30 and the HART modem module 40 can transmit signals in two directions, and the CPU module 30 performs corresponding signal processing on the demodulated separated HART signal, thereby obtaining a feedback signal and sending the feedback signal back to the HART modem module 40 for modulation again. Subsequently, the HART output coupling module 50 receives the modulated feedback signal for coupling, couples the feedback signal to 4mA to 20mA, and outputs the feedback signal to the outside through the intrinsically safe input/output module 10.

The respective modules in this embodiment will now be explained:

referring first to fig. 2, in the present embodiment, the intrinsically safe input/output module 10 may be divided into two circuits, namely, a protection circuit and a filtering EMC suppression circuit. For the HART signals inputted from the outside, they are inputted to the HART input isolation module 20 after passing through the protection circuit and the filtering EMC suppression circuit in sequence, and for the HART signals outputted to the outside, they are outputted to the outside after passing through the filtering EMC suppression circuit and the protection circuit in sequence. The externally input signal is (4-20) mA and HART signal after the superposition.

Specifically, the protection circuit includes a TVS tube TVS1, a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, and a fuse F1. The model of the TVS tube is SMBJ36CA to play an overvoltage protection role, the first diode D1, the second diode D2, the third diode D3, the fourth diode D4 and the fifth diode D5 are Schottky diodes, the Schottky diodes are arranged mainly for matching with intrinsic safety equipment of other external inputs and power supply direction protection, and the fuse F1 plays a current limiting role. The input superposed HART signal enters the filtering EMC suppression circuit through a first diode D1, a second diode D2, a third diode D3 and a fuse F1 which are arranged in series in sequence, and the feedback signal input from the filtering EMC suppression circuit after superposition enters the protection circuit and is directly output. The superimposed HART signals are all output from the positive inputs and the negative inputs of the first diode D1, the second diode D2 and the third diode D3. The TVS transistor TVS1, the fourth diode D4 and the fifth diode D5 are connected in parallel. One end of the TVS1 is electrically connected to the positive electrode of the first diode D1, i.e., directly connected to the input terminal of the protection circuit, the other end of the first diode D1 is electrically connected to the output terminal of the protection circuit, the positive electrode of the fourth diode D4, and the positive electrode of the fifth diode D5, respectively, and the negative electrode of the fourth diode D4 and the negative electrode of the fifth diode D5 are connected to the fuse F1.

Referring to fig. 2, the filtering EMC suppression circuit includes a first BL1, a second BL2, a connector L3, a first capacitor C1, a first resistor R1, a first inductor L1, and a second inductor L2. The HART signal superimposed from the protection circuit is outputted from the filtering EMC suppression circuit after passing through the first BL1, the connector L3 and the first inductor L1 in sequence. The superimposed feedback signal input from the HART output coupling module 50 enters the protection circuit through the second inductor L2, the connector L3 and the second BL2 in sequence. The circuit is connected with a connector L3 by 4 lines, the 4 lines are respectively connected with a first BL1, a second BL2, a first inductor L1 and a second inductor L2, the line connected with the first inductor L1 is also electrically connected with a first capacitor C1, the line connected with the second inductor L2 is also electrically connected with a first resistor R1, and the first capacitor C1 and the first resistor R1 are arranged in series.

Referring to fig. 2, in the present embodiment, the HART input isolation module 20 includes a second resistor R2 and a DC-DC converter, and the second resistor R2 plays an isolation role. The superimposed HART signal inputted from the first inductor L1 is divided into two paths before passing through the second resistor R2, wherein one path sequentially passes through the second resistor R2 and the DC-DC converter to output 3V DC power, which provides power support for this embodiment, and the other path inputs the HART signal into the HART modem module 40.

Referring to fig. 3, HART modem module 40 may be considered to be comprised of a HART modem. As described above, in the present embodiment, the HART modem uses a high-quality HART modem chip. The input HART signal enters the HART modem after sequentially passing through the intrinsic safety energy limiting circuit and the signal filtering circuit.

Referring to fig. 3, the intrinsically safe power limiting circuit includes a third resistor R3, a second capacitor C2, a first regulator tube Z1, and a second regulator tube Z2. HART signals enter the signal filtering circuit after sequentially passing through a third resistor R3 and a second capacitor C2 which are arranged in series, and a first voltage-regulator tube Z1 and a second voltage-regulator tube Z2 are arranged in parallel and are also arranged in parallel with the second capacitor C2. The negative electrode of the first voltage-regulator tube Z1 and the negative electrode of the second voltage-regulator tube Z2 are electrically connected with the second capacitor, and the positive electrode of the first voltage-regulator tube Z1 and the positive electrode of the second voltage-regulator tube Z2 are both grounded.

Referring to fig. 3, the signal filtering circuit includes a fourth resistor R4, a third capacitor C3, and a fourth capacitor C4. The HART signal will enter the HART modem through the fourth resistor R4 and the third capacitor C3 in turn. The fourth capacitor C4 is disposed between the fourth resistor R4 and the third capacitor C3, and is disposed in parallel with the third capacitor C3, one end of the fourth capacitor C4 is electrically connected to the third capacitor C3 and the fourth resistor R4, respectively, and the other end is grounded.

Preferably, referring to fig. 4, the intrinsically safe energy limiting circuit further includes a first amplifying circuit, the first amplifying circuit is disposed between the third resistor R3 and the second capacitor C2, and the first amplifying circuit includes a fifth capacitor C5, a sixth capacitor C6, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, and a first operational amplifier U1. The first amplifying circuit can realize signal amplification and has an isolation effect, wherein the fifth resistor R5 and the sixth resistor R6 are bias resistors, the seventh resistor R7 and the eighth resistor R8 are amplification feedback resistors, the amplification factor is 1+ R8/R7, and the amplitude of HART signals can be adjusted only by adjusting the sizes of the seventh resistor R7 and the eighth resistor R8. The HART signal first enters the fifth capacitor C5 and then enters the non-inverting input of the first operational amplifier U1, and the sixth resistor R6 is arranged in parallel with the fifth resistor R5 and is electrically connected to the output of the fifth capacitor. The positive power supply end of the first operational amplifier U1 is connected to a 3V power supply, and the power supply current also passes through a fifth resistor R5 and a sixth capacitor and then is grounded. The inverting input terminal of the first operational amplifier U1 is electrically connected to a seventh resistor R7 and an eighth resistor R8, which are arranged in parallel, the other terminal of the seventh resistor R7 is grounded, the other terminal of the eighth resistor R8 is electrically connected to the output terminal of the first operational amplifier U1 and one terminal of a ninth resistor R9, respectively, the other terminal of the ninth resistor R9 is electrically connected to the second capacitor C2, and the amplified HART signal is output.

The HART modem chip and its peripheral circuits of the HART modem are not specifically explained. The HART modem sends the demodulated data signal to the CPU module 30 for data processing through the UART communication port HART-RXD, and the CPU module 30 feeds back the related data to the HART modem module 40 for modulation through the HART communication port HART-TXD after data processing, and then the modulated feedback signal can be obtained. The feedback signal is actually a HART signal and is named feedback signal to distinguish it from the input signal.

Referring to fig. 3, HART output coupling module 50 includes a current limiting isolation circuit and a coupling circuit. The modulated feedback signal is sent to the intrinsically safe input/output module 10 after passing through the current limiting isolation circuit and the coupling circuit in sequence, so as to output a signal.

Referring to fig. 3, the current-limiting isolation circuit includes a seventh capacitor C7 and a tenth resistor R10 connected in series to perform a current-limiting isolation function, and the feedback signal sequentially passes through the seventh capacitor C7 and the tenth resistor R10 and then enters the coupling circuit.

Referring to fig. 3, the coupling circuit includes an eleventh resistor R11, a twelfth resistor R12, a thirteenth resistor R13, a third regulator tube Z3, a fourth regulator tube Z4, and a field effect tube Q1. The third voltage regulator tube Z3 and the fourth voltage regulator tube Z4 play a role in overvoltage protection, the eleventh resistor R11 and the twelfth resistor R12 are bias resistors, and the field effect tube Q1 couples the feedback signal to a (4-20) mA signal and then outputs the mA signal. And the eleventh resistor R11, the twelfth resistor R12, the third voltage regulator tube Z3, the fourth voltage regulator tube Z4 and the field effect tube Q1 are arranged in parallel. One end of an eleventh resistor R11, one end of a twelfth resistor R12, the cathode of the third voltage regulator tube Z3, the cathode of the fourth voltage regulator tube Z4 and the grid of the field effect tube Q1 are electrically connected and are associated with a circuit through which a feedback signal passes. The other end of the eleventh resistor R11, the anode of the third voltage regulator tube Z3 and the anode of the fourth voltage regulator tube Z4 are all grounded, and the other end of the twelfth resistor R12 is electrically connected with a power supply. The drain of the field effect transistor Q1 is electrically connected with one end of the thirteenth resistor R13, the other end of the thirteenth resistor R13 is grounded, and the source of the field effect transistor Q1 is the output end of the coupling circuit.

Advantageously, referring to fig. 5, a second amplifying circuit is further disposed in series between the seventh capacitor C7 and the tenth resistor R10, and the second amplifying circuit includes a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, a seventeenth resistor R17, an eighth capacitor C8, and a second operational amplifier U2. Similarly to the first amplifying circuit, the fourteenth resistor R14 and the fifteenth resistor R15 are bias resistors, and the sixteenth resistor R16 and the seventeenth resistor R17 are amplifying feedback resistors. After entering from the seventh capacitor C7, the feedback signal is biased by a fourteenth resistor R14 and a fifteenth resistor R15 arranged in parallel and enters the non-inverting input terminal of the second operational amplifier U2. The inverting input terminal of the second operational amplifier U2 is electrically connected to a sixteenth resistor R16 and a seventeenth resistor R17, which are connected in parallel, respectively, the other terminal of the sixteenth resistor R16 is grounded, the other terminal of the seventeenth resistor R17 is electrically connected to the output terminal of the second operational amplifier U2 and one terminal of an eighth capacitor C8, and the other terminal of the eighth capacitor C8 is connected to the tenth resistor R10.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, it is still within the scope of the present invention if they fall within the scope of the claims of the present invention and their equivalents.