Constant current communication circuit, communication device and communication system

Abstract

The utility model discloses a constant current communication circuit, a communication device and a communication system, the constant current communication circuit comprises a constant current circuit, the controlled end of the constant current circuit is used for accessing a communication signal output by a sending device, and the ground end of the constant current circuit is grounded; a current sampling circuit; the constant current circuit is used for controlling the current flowing through the current sampling circuit to be constant when the communication signal is at the first level, and controlling the current flowing through the current sampling circuit to be zero when the communication signal is at the second level; the first input end of the conversion receiving circuit and the second input end of the conversion receiving circuit are connected to the two ends of the current sampling circuit in parallel respectively, the output end of the conversion receiving circuit is electrically connected with receiving equipment, and the conversion receiving circuit is used for converting the state of the current flowing through the current sampling circuit into a corresponding level and outputting the level to the receiving equipment; the technical scheme of the utility model aims to reduce the interference of the external environment on the communication line and improve the stability and reliability of communication.

Description

Technical Field

[0001] The utility model relates to the technical field of communication circuits, and in particular to a constant current communication circuit, a communication device and a communication system. Background Art

[0002] At present, the existing communication protocols are often faced with the challenge of how to ensure the accuracy and reliability of information transmission when they are designed. Communications such as 485 and 232 are very susceptible to the influence of the external environment, especially in complex practical application scenarios such as electromagnetic interference and temperature changes. These factors may cause the level to change during transmission, causing the communication signal to be distorted or interrupted, thereby affecting the stability and reliability of the communication. Utility Model Content

[0003] The main purpose of the utility model is to provide a constant current communication circuit, a communication device and a communication system, aiming to reduce the interference of the external environment on the communication line and improve the stability and reliability of the communication.

[0004] To achieve the above purpose, the constant current communication circuit proposed by the utility model is connected in series between the sending device and the receiving device, and the constant current communication circuit includes:

[0005] A constant current circuit, wherein a controlled end of the constant current circuit is used to access the communication signal output by the sending device, and a ground end of the constant current circuit is grounded;

[0006] A current sampling circuit, wherein the input end of the current sampling circuit is used to access the first power supply, and the output end of the current sampling circuit is connected to the input end of the constant current circuit;

[0007] The constant current circuit is used to control the current flowing through the current sampling circuit to be constant when the communication signal is at a first level, and to control the current flowing through the current sampling circuit to be zero when the communication signal is at a second level, wherein the first level is different from the second level;

[0008] A conversion receiving circuit, wherein the first input terminal of the conversion receiving circuit and the second input terminal of the conversion receiving circuit are respectively connected in parallel to the two ends of the current sampling circuit, and the output terminal of the conversion receiving circuit is electrically connected to the receiving device, and is used to convert the current state flowing through the current sampling circuit into a corresponding level and output it to the receiving device.

[0009] In some embodiments, the constant current circuit comprises:

[0010] A first clamping circuit, wherein an input end of the first clamping circuit is used to connect to the transmitting device, and an output end of the first clamping circuit is grounded;

[0011] a second clamping circuit, wherein an input end of the second clamping circuit is connected to an output end of the current sampling circuit, a controlled end of the second clamping circuit is connected to a control end of the first clamping circuit, a ground end of the second clamping circuit is grounded, and a control end of the second clamping circuit is connected to a controlled end of the first clamping circuit;

[0012] The first clamping circuit is used for, when the connected communication signal is at a first level, dividing the first level into a corresponding control voltage to control the state of the second clamping circuit;

[0013] The second clamping circuit is used to adjust the voltage division of the first clamping circuit according to the current flowing through the current sampling circuit to adjust the control voltage, and to adjust the current limiting of the current according to the control voltage to maintain the current constant.

[0014] In some embodiments, the first clamping circuit comprises:

[0015] a first resistor, wherein a first end of the first resistor is an input end of the first clamping circuit;

[0016] A first switch tube, wherein the input end of the first switch tube is the control end of the first clamp circuit and is connected to the second end of the first resistor, the output end of the first switch tube is grounded, and the controlled end of the first switch tube is the controlled end of the first clamp circuit.

[0017] In some embodiments, the first switch tube includes a triode.

[0018] In some embodiments, the second clamping circuit comprises:

[0019] a second switch tube, wherein an input end of the second switch tube is an input end of the second clamp circuit, an output end of the second switch tube is a control end of the second clamp circuit, and a controlled end of the second switch tube is a controlled end of the second clamp circuit;

[0020] A second resistor is connected in series between the output end of the second switch tube and the ground.

[0021] In some embodiments, the current sampling circuit includes:

[0022] A third resistor is connected in series between the first input terminal of the conversion receiving circuit and the second input terminal of the conversion receiving circuit.

[0023] In some embodiments, the conversion receiving circuit includes:

[0024] An operational amplifier, comprising a power pin, a ground pin, a non-inverting input pin, an inverting input pin and an output pin, wherein the power pin is used to connect to the first power supply, the ground pin is grounded, and the output pin is the output end of the conversion receiving circuit;

[0025] a fourth resistor and a fifth resistor, wherein the first end of the fourth resistor is used to connect to the first power supply, the second end of the fourth resistor is connected to the inverting input pin, and the fifth resistor is connected in series between the output end of the constant current circuit and the non-inverting input pin;

[0026] A sixth resistor, connected in series between the inverting input pin and ground;

[0027] a seventh resistor connected in parallel to the positive phase input pin and the output pin;

[0028] An eighth resistor is connected in series between the output pin and the receiving device.

[0029] In some embodiments, the conversion receiving circuit further includes:

[0030] A clamping tube, wherein the cathode of the clamping tube is used to be connected to the second power supply, and the anode of the clamping tube is connected to the second end of the eighth resistor.

[0031] The utility model also provides a communication device, which includes the above-mentioned constant current communication circuit.

[0032] The utility model also provides a communication system, including a sending device, a receiving device, and the above-mentioned constant current communication circuit.

[0033] The technical solution of the utility model adopts a constant current circuit to realize communication, converts voltage transmission into current transmission, and utilizes the principle that the current is equal everywhere in the series circuit. The current value in the entire transmission cable is controlled to be constant through the constant current circuit, and a constant current value and 0 current are used to replace the first level and the second level in the voltage transmission. Finally, different current states are converted into corresponding levels by converting the receiving circuit, and are received by the receiving device. By maintaining the stability of the current to resist external interference, the anti-interference ability and stability of the communication are significantly improved, and the risk of changes in the transmission level due to the influence of the external environment during communication of the equipment, causing distortion or interruption of the communication signal, and causing communication packet loss and error packet problems is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0035] Figure 1 This is a structural schematic diagram of an embodiment of a constant current communication circuit of the utility model;

[0036] Figure 2 It is a structural schematic diagram of another embodiment of the constant current communication circuit of the utility model;

[0037] Figure 3 This is a schematic diagram of the structure of an embodiment of the communication device of the utility model;

[0038] Figure 4 This is a circuit connection diagram of an embodiment of a constant current communication circuit of the utility model;

[0039] Figure 5 This is a schematic diagram of the regulation of the constant current communication circuit of the utility model.

[0040] Description of Figure Numbers:

[0041] Label name Label name 100 Constant current communication circuit 200 Sending device 110 Constant current circuit 300 Receiving equipment 111 First clamp circuit U1 Operational Amplifier 112 Second clamp circuit TZ1 Clamp tube 120 Current sampling circuit Q1~Q2 The first switch tube ~ the second switch tube 130 Converting receiving circuit R1~R8 The first resistor to the eighth resistor

[0042] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0044] In addition, in the present utility model, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present utility model.

[0045] The utility model provides a constant current communication circuit.

[0046] Reference Figure 1 In one embodiment, the constant current communication circuit is connected in series between the sending device and the receiving device, and includes:

[0047] A constant current circuit 110, wherein a controlled end of the constant current circuit 110 is used to access the communication signal output by the transmitting device, and a ground end of the constant current circuit 110 is grounded;

[0048] A current sampling circuit 120, wherein the input end of the current sampling circuit 120 is used to access the first power supply, and the output end of the current sampling circuit 120 is connected to the input end of the constant current circuit 110;

[0049] The constant current circuit 110 is used to control the current flowing through the current sampling circuit 120 to be constant when the communication signal is at a first level, and to control the current flowing through the current sampling circuit 120 to be zero when the communication signal is at a second level, wherein the first level is different from the second level;

[0050] A conversion receiving circuit 130, wherein a first input terminal of the conversion receiving circuit 130 and a second input terminal of the conversion receiving circuit 130 are respectively connected in parallel to two ends of the current sampling circuit 120, and an output terminal of the conversion receiving circuit 130 is electrically connected to the receiving device, and is used to convert the current state flowing through the current sampling circuit 120 into a corresponding level and output it to the receiving device.

[0051] It should be noted that when performing long-distance wired transmission, communication devices are connected by cables. The conventional communication transmission method is voltage signal transmission. The communication data is transmitted by combining the first level and the second level in different ways and using the voltage signal of the corresponding level combination. However, due to the use of voltage transmission, there will be voltage drop loss on the cable, and as the external environment changes, the cable's loss of voltage signal will also change. For example, the voltage drop of the cable is different at different temperatures, etc. This may cause the level to change during transmission, causing the communication signal to be distorted or interrupted, thereby affecting the stability and reliability of the communication.

[0052] In this embodiment, the constant current circuit 110 may have various structures, including but not limited to two switching tubes that restrain each other, or an operational amplifier circuit with a constant current function, etc.

[0053] Specifically, the communication devices that communicate with each other are divided into a sending device and a receiving device. When the sending device sends a communication signal to the receiving device, the communication signal may be a first level or a second level. If the communication signal is a first level, the constant current circuit 110 is turned on after the controlled end is connected to the first level, so that the first power flows through the current sampling circuit 120, the constant current circuit 110 to the ground to form a current loop. The current in the current loop is controlled by the constant current circuit 110 and maintained at a constant current value, wherein the constant current value can be preset by the R&D personnel, or determined by the model of the device inside the constant current circuit 110, and the constant current value is not 0. The current sampling circuit 120 samples the constant current value and outputs the corresponding current sampling signal to the conversion receiving circuit 130, which is output as a corresponding level, such as the first level, according to the constant current value through the conversion receiving circuit 130.

[0054] If the communication signal is at the second level, the constant current circuit 110 is turned off after the controlled end is connected to the second level, and the above-mentioned current loop is disconnected, so that the current value flowing through the current sampling circuit 120 is zero. At this time, the current sampling circuit 120 samples the zero current and outputs the corresponding current sampling signal to the conversion receiving circuit 130, which is output as a corresponding level, such as the second level, according to the constant current value through the conversion receiving circuit 130.

[0055] The technical solution of the utility model adopts a constant current circuit 110 to realize communication, converts voltage transmission into current transmission, and utilizes the principle that the current is equal everywhere in the series circuit. The constant current circuit 110 controls the current value in the entire transmission cable to be constant, and replaces the first level and the second level in the voltage transmission with a constant current value and 0 current. Finally, the different current states are converted into corresponding levels by the conversion receiving circuit 130, which are received by the receiving device. By maintaining the stability of the current to resist external interference, the anti-interference ability and stability of the communication are significantly improved, and the risk of changes in the transmission level due to the influence of the external environment during communication of the equipment is reduced, causing distortion or interruption of the communication signal, and causing communication packet loss and error packet problems.

[0056] Reference Figure 2 and Figure 4 In one embodiment, the constant current circuit 110 includes:

[0057] A first clamping circuit 111, wherein an input end of the first clamping circuit 111 is used to connect to the transmitting device, and an output end of the first clamping circuit 111 is grounded;

[0058] a second clamping circuit 112, wherein an input end of the second clamping circuit 112 is connected to an output end of the current sampling circuit 120, a controlled end of the second clamping circuit 112 is connected to a control end of the first clamping circuit 111, a ground end of the second clamping circuit 112 is grounded, and a control end of the second clamping circuit 112 is connected to a controlled end of the first clamping circuit 111;

[0059] The first clamping circuit 111 is used for, when the received communication signal is at a first level, dividing the first level into a corresponding control voltage to control the state of the second clamping circuit 112;

[0060] The second clamp circuit 112 is used to adjust the voltage division of the first clamp circuit 111 according to the current flowing through the current sampling circuit 120 to adjust the control voltage, and to adjust the current limiting of the current according to the control voltage to maintain the current constant.

[0061] In this embodiment, the first level is higher than the second level.

[0062] When the transmitting device sends a communication signal to the receiving device, if the communication signal is at the first level, the first clamp circuit 111 divides the first level, outputs the corresponding control voltage, and turns on the second clamp circuit 112, so that the first power flows through the current sampling circuit 120 and the second clamp circuit 112 to the ground to form a current loop. At the same time, the second clamp circuit 112 outputs a regulating voltage that is proportional to the current in the current loop. If the current in the current loop is greater than the constant current value at this time, the voltage value of the regulating voltage will also increase, and the voltage division ratio inside the first clamp circuit 111 is adjusted to reduce the control voltage output by the first clamp circuit 111, so that the second clamp circuit 112 increases its current limiting capacity under the control of the control voltage, so that the current value of the current loop is reduced. When the current in the current loop is less than the constant current value, the same applies until the current in the current loop stabilizes at the constant current value.

[0063] If the communication signal is at the second level, the first clamp circuit 111 cannot reach the minimum voltage value of the control voltage of the second clamp level after dividing the second level, so the second clamp level is turned off, and the above-mentioned current loop is disconnected, so that the current value flowing through the current sampling circuit 120 is zero.

[0064] Specifically, the first clamping circuit 111 includes:

[0065] A first resistor R1, wherein a first end of the first resistor R1 is an input end of the first clamping circuit 111;

[0066] A first switch tube Q1, wherein the input end of the first switch tube Q1 is the control end of the first clamp circuit 111 and is connected to the second end of the first resistor R1, the output end of the first switch tube Q1 is grounded, and the controlled end of the first switch tube Q1 is the controlled end of the first clamp circuit 111.

[0067] The second clamping circuit 112 comprises:

[0068] a second switch tube Q2, wherein the input end of the second switch tube Q2 is the input end of the second clamp circuit 112, the output end of the second switch tube Q2 is the control end of the second clamp circuit 112, and the controlled end of the second switch tube Q2 is the controlled end of the second clamp circuit 112;

[0069] The second resistor R2 is connected in series between the output end of the second switch tube Q2 and the ground.

[0070] In this embodiment, the first switch tube Q1 and the second switch tube Q2 are NPN transistors, the first level is a high level, and the second level is a low level.

[0071] When the communication signal sent is at a high level, the first resistor R1 divides the high level. Since the divided voltage is higher than the conduction voltage of the PN junction of the second switch tube Q2, the PN junction is forward biased, and the second switch tube Q2 is set in an amplification state. At this time, the second switch tube Q2 is turned on, so that the first power source flows through the current sampling circuit 120, the second switch tube Q2, the second resistor R2 to the ground to form a current loop, and the current flowing through the second switch tube Q2 is controlled by the base current of the second switch tube Q2.

[0072] Since the current loop is connected, the base of the first switch tube Q1 is also controlled by the voltage across the second resistor R2 and works in an amplification state, and its equivalent internal resistance and the first resistor R1 jointly divide the connected high level, and the control voltage connected to the second switch tube Q2 is the voltage drop of the equivalent resistance of the first resistor R1.

[0073] like Figure 5As shown, if the current in the current loop is greater than the constant current value at this time, the voltage value across the second resistor R2 will also increase, so that the adjustment voltage connected to the first switch tube Q1 increases. At this time, in order to increase the conduction degree of the first switch tube Q1, that is, to increase the current flowing through the first switch tube Q1, the equivalent resistance in the first switch tube Q1 will decrease. Then, the voltage division ratio of the first resistor R1 and the equivalent resistance in the first switch tube Q1 increases, so that the voltage division of the equivalent resistance in the first switch tube Q1 decreases, and the control voltage input to the second switch tube Q2 is reduced. At this time, the equivalent resistance in the second switch tube Q2 will increase, so that the conduction degree of the second switch tube Q2 decreases with the control voltage, and then the current flowing through the second switch tube Q2 decreases. When the current in the current loop is less than the constant current value, the working states of the first switch tube Q1 and the second switch tube Q2 are similar, until the current in the current loop stabilizes at the constant current value.

[0074] If the communication signal is at a low level, then after voltage division by the first resistor R1, the low level cannot reach the minimum voltage value of the control voltage of the second switch tube Q2, so the second switch tube Q2 is turned off, and the above-mentioned current loop is disconnected, so that the current value flowing through the current sampling circuit 120 is zero.

[0075] The utility model realizes communication through current transmission. Voltage-type communication transmission makes high and low levels susceptible to external interference, resulting in level changes. However, in current-type communication transmission, due to the existence of the constant current circuit 110, changes in external interference will be offset by the constant current circuit 110, which can reduce communication packet loss and error problems caused by external interference.

[0076] Reference Figure 1 and Figure 4 In one embodiment, the current sampling circuit 120 includes:

[0077] The third resistor R3 is connected in series between the first input terminal of the conversion receiving circuit 130 and the second input terminal of the conversion receiving circuit 130 .

[0078] In this embodiment, the third resistor R3 is a current sampling resistor, and since the voltage across the resistor complies with Ohm's law, the voltage across the third resistor R3 can be collected to convert the current value flowing through the third resistor R3.

[0079] Reference Figure 1 and Figure 4 In one embodiment, the conversion receiving circuit 130 includes:

[0080] The operational amplifier U1 has a power pin, a ground pin, a non-inverting input pin, an inverting input pin and an output pin, wherein the power pin is used to connect to the first power supply, the ground pin is grounded, and the output pin is the output end of the conversion receiving circuit 130;

[0081] A fourth resistor R4 and a fifth resistor R5, wherein a first end of the fourth resistor R4 is used to connect to the first power supply, a second end of the fourth resistor R4 is connected to the inverting input pin, and the fifth resistor R5 is connected in series between the output end of the constant current circuit 110 and the non-inverting input pin;

[0082] A sixth resistor R6, connected in series between the inverting input pin and ground;

[0083] a seventh resistor R7, connected in parallel to the non-inverting input pin and the output pin;

[0084] An eighth resistor R8 is connected in series between the output pin and the receiving device.

[0085] In this embodiment, the operational amplifier U1 and the fourth resistor R4, the fifth resistor R5, the sixth resistor R6, the seventh resistor R7, and the eighth resistor R8 together form a differential amplifier circuit, wherein the fourth resistor R4 and the fifth resistor R5 are differential resistors, the sixth resistor R6 is a pull-down resistor of the inverting input pin, the seventh resistor R7 is a feedback resistor of the operational amplifier U1, and the eighth resistor R8 is a current limiting resistor of the output pin.

[0086] When the conversion receiving circuit 130 is working, the operational amplifier U1 collects the voltage values ​​at both ends of the third resistor R3 through the non-phase input pin and the inverting input pin respectively, and performs differential processing on the two collected voltage values ​​to obtain the voltage division value of the third resistor R3 as the current collection signal, and amplifies the current collection signal and outputs it to the receiving device.

[0087] When the current flowing through the current sampling circuit 120 is a constant current value, the current acquisition signal is the voltage division value of the third resistor R3. When the current flowing through the current sampling circuit 120 is zero, the current acquisition signal is 0, so that the current state flowing through the current sampling circuit 120 can be converted into a corresponding level and output to the receiving device.

[0088] Reference Figure 1 and Figure 4 In one embodiment, the conversion receiving circuit 130 further includes:

[0089] The clamping tube TZ1 has a cathode connected to a second power supply, and an anode connected to the second end of the eighth resistor R8.

[0090] In this embodiment, the clamping tube TZ1 is used to clamp the level when the voltage value of the level output by the conversion receiving circuit 130 exceeds the voltage value corresponding to the second power supply, so that it does not exceed the voltage value corresponding to the second power supply, thereby preventing the signal interface of the receiving device from being damaged by voltage shock.

[0091] The utility model also proposes a communication device, which includes the above-mentioned constant current communication circuit 100. The specific structure of the constant current communication circuit 100 refers to the above-mentioned embodiment. Since the communication device adopts all the technical solutions of all the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.

[0092] Reference Figure 3 The utility model also proposes a communication system, which includes a sending device 200 and a receiving device 300, as well as the above-mentioned constant current communication circuit 100. The specific structure of the constant current communication circuit 100 refers to the above-mentioned embodiment. Since the communication system adopts all the technical solutions of all the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here one by one.

[0093] The above description is only an optional embodiment of the utility model, and does not limit the patent scope of the utility model. All equivalent structural changes made by using the contents of the utility model specification and drawings under the utility model concept, or directly / indirectly used in other related technical fields are included in the patent protection scope of the utility model.

Claims

1. A constant current communication circuit, connected in series between a sending device and a receiving device, characterized in that: The constant current communication circuit comprises: A constant current circuit, wherein a controlled end of the constant current circuit is used to access the communication signal output by the sending device, and a ground end of the constant current circuit is grounded; A current sampling circuit, wherein the input end of the current sampling circuit is used to access the first power supply, and the output end of the current sampling circuit is connected to the input end of the constant current circuit; The constant current circuit is used to control the current flowing through the current sampling circuit to be constant when the communication signal is at a first level, and to control the current flowing through the current sampling circuit to be zero when the communication signal is at a second level; wherein the first level is different from the second level; A conversion receiving circuit, wherein the first input terminal of the conversion receiving circuit and the second input terminal of the conversion receiving circuit are respectively connected in parallel to the two ends of the current sampling circuit, and the output terminal of the conversion receiving circuit is electrically connected to the receiving device, and is used to convert the current state flowing through the current sampling circuit into a corresponding level and output it to the receiving device.

2. The constant current communication circuit according to claim 1, characterized in that: The constant current circuit comprises: A first clamping circuit, wherein an input end of the first clamping circuit is used to connect to the transmitting device, and an output end of the first clamping circuit is grounded; a second clamping circuit, wherein an input end of the second clamping circuit is connected to an output end of the current sampling circuit, a controlled end of the second clamping circuit is connected to a control end of the first clamping circuit, a ground end of the second clamping circuit is grounded, and a control end of the second clamping circuit is connected to a controlled end of the first clamping circuit; The first clamping circuit is used for, when the connected communication signal is at a first level, dividing the first level into a corresponding control voltage to control the state of the second clamping circuit; The second clamping circuit is used to adjust the voltage division of the first clamping circuit according to the current flowing through the current sampling circuit to adjust the control voltage, and to adjust the current limiting of the current according to the control voltage to maintain the current constant.

3. The constant current communication circuit as claimed in claim 2, characterized in that: The first clamping circuit comprises: a first resistor, wherein a first end of the first resistor is an input end of the first clamping circuit; A first switch tube, wherein the input end of the first switch tube is the control end of the first clamp circuit and is connected to the second end of the first resistor, the output end of the first switch tube is grounded, and the controlled end of the first switch tube is the controlled end of the first clamp circuit.

4. The constant current communication circuit as claimed in claim 3, characterized in that: The first switch tube includes a triode.

5. The constant current communication circuit according to claim 2, characterized in that: The second clamping circuit comprises: a second switch tube, wherein an input end of the second switch tube is an input end of the second clamp circuit, an output end of the second switch tube is a control end of the second clamp circuit, and a controlled end of the second switch tube is a controlled end of the second clamp circuit; A second resistor is connected in series between the output end of the second switch tube and the ground.

6. The constant current communication circuit according to claim 1, characterized in that: The current sampling circuit comprises: A third resistor is connected in series between the first input terminal of the conversion receiving circuit and the second input terminal of the conversion receiving circuit.

7. The constant current communication circuit according to claim 1, characterized in that: The conversion receiving circuit comprises: An operational amplifier, comprising a power pin, a ground pin, a non-inverting input pin, an inverting input pin and an output pin, wherein the power pin is used to connect to the first power supply, the ground pin is grounded, and the output pin is the output end of the conversion receiving circuit; a fourth resistor and a fifth resistor, wherein the first end of the fourth resistor is used to connect to the first power supply, the second end of the fourth resistor is connected to the inverting input pin, and the fifth resistor is connected in series between the output end of the constant current circuit and the non-inverting input pin; A sixth resistor, connected in series between the inverting input pin and ground; a seventh resistor connected in parallel to the positive phase input pin and the output pin; An eighth resistor is connected in series between the output pin and the receiving device.

8. The constant current communication circuit according to claim 7, characterized in that: The conversion receiving circuit also includes: A clamping tube, wherein the cathode of the clamping tube is used to be connected to the second power supply, and the anode of the clamping tube is connected to the second end of the eighth resistor.

9. A communication device, characterized in that: The communication device comprises a constant current communication circuit as described in any one of claims 1-8.

10. A communication system, characterized in that: It comprises a sending device and a receiving device, and a constant current communication circuit as described in any one of claims 1 to 8.

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