CN213751061U

CN213751061U - RS485 bus protection circuit in integrated circuit

Info

Publication number: CN213751061U
Application number: CN202022428179.4U
Authority: CN
Inventors: 单伟; 汪爱梅; 宋少伟
Original assignee: Senyang Automotive Technology Tianjin Co ltd
Current assignee: Senyang Automotive Technology Tianjin Co ltd
Priority date: 2020-10-28
Filing date: 2020-10-28
Publication date: 2021-07-20
Anticipated expiration: 2030-10-28

Abstract

The utility model provides a RS485 bus protection circuit among integrated circuit, including keeping apart power module N1, RS485 communication chip N3, singlechip chip N4, ADC _03 detection circuitry, keep apart power module N1's GND foot ground IN, N1's IN foot is connected with triode T17's projecting pole, and the OUT foot output steady voltage VCC _3V3 of N1 does RS485 communication chip N3, singlechip chip N4 power supply, protection circuit can effectively protect the broken ring of short circuit transient state high current to RS485 communication line, protects RS485 serial bus, has guaranteed the steady operation of RS485 serial bus.

Description

RS485 bus protection circuit in integrated circuit

Technical Field

The utility model belongs to the technical field of the communication and specifically relates to a RS485 bus protection circuit among integrated circuit.

Background

Along with the development of society, "intelligence" has been full of human daily life, and integrated circuit has played a huge effect in every industry, and RS485 can satisfy the requirement that communication distance is far away, interference killing feature is big, transmission rate is high. The intelligent devices connected through the RS485 bus can form a network topology, and the requirement of network informatization is met. One host can control a plurality of slave machines simultaneously, and the one-to-many master-slave communication mode greatly improves the communication efficiency and saves the cost.

However, due to the existence of various factors, the short circuit of the power supply is often caused, so that the current of the integrated circuit is suddenly overloaded, and the RS485 serial bus is damaged and cannot work normally. In addition, in practical application, for example, the situations of improper operation of personnel, overlarge load, aging of a line, looseness caused by vibration and the like occur, and even static electricity introduced in an irregular way can introduce higher instantaneous voltage to damage a communication circuit of the RS485 serial bus. Therefore, necessary protection measures must be introduced to ensure stable operation of the RS485 serial bus.

SUMMERY OF THE UTILITY MODEL

The utility model aims to solve the technical problem that a RS485 bus protection circuit among integrated circuit is provided.

In order to solve the technical problem, the technical scheme of the utility model is that:

an RS485 bus protection circuit IN an integrated circuit comprises an isolation power supply module N1, an RS485 communication chip N3, a single chip microcomputer chip N4 and an ADC _03 detection circuit, wherein a GND pin of the isolation power supply module N1 is connected with the inside, an IN pin of the N1 is connected with an emitter of a triode T17, and an OUT pin of the N1 outputs a stable voltage VCC _3V3 to supply power for the RS485 communication chip N3 and the single chip microcomputer chip N4; a pin 1 of the RS485 communication chip N3 is connected with a pin UART1_ RX of a singlechip chip N4, a pin 2 of the RS485 communication chip N3 is connected with a pin RE of the singlechip chip N4, a pin 3 of the RS485 communication chip N3 is connected with a pin DE of the singlechip chip N4, a pin 4 of the RS485 communication chip N3 is connected with a pin UART1_ TX of the singlechip chip N4 at the end connected with the ground, a pin 5 of the RS485 communication chip N3 is connected with the ground, a pin 6 and a pin 7 of the RS485 communication chip N3 are sequentially connected with an external wiring socket 485A and an external wiring socket 485B end, and a pin 8 of the RS485 communication chip N3 is connected with 3.3V output by an isolation power supply module N1;

pins

1, 9, 24 and 48 of the singlechip chip N4 are all pulled up to 3.3V for power supply and are connected with the ground through capacitors C53, C57, C58 and C52; for clarity of connection, 17 pins (ADC _ IN7) are coded as ADC03, 30 pins are coded as UART1_ TX, 31 pins are coded as UART1_ RX, 33 pins (I/O ports) are coded as RE, 35 pins (I/O ports) are coded as RS485_ EN, and 36 pins (I/O ports) are coded as DE; the ADC _03 detection circuit adopts a voltage value at the negative pole of the integrated circuit in a series resistance voltage division mode and transmits the voltage value to an ADC03 pin of the single chip microcomputer chip N4.

Preferably, in the RS485 bus protection circuit in the integrated circuit, pin 7 of the RS485 communication chip N3 is connected to the resistor R101; and the pin 8 of the RS485 communication chip N3 is connected with the resistor R102 and used for limiting current.

Preferably, the RS485 bus protection circuit in the integrated circuit further includes a MOS transistor M5 and a MOS transistor M6, a source of the MOS transistor M5 is connected in series with the resistor R101, a gate of the MOS transistor M5 is connected with the control terminal circuit connection identifier PRS485 and the resistor R106, and a drain of the MOS transistor M5 is connected with the external connection jack 485B; the source electrode of the MOS tube M6 is connected with the resistor R102 in series, the grid electrode of the MOS tube M6 is connected with the control end line connection mark PRS485 and the resistor R106, and the drain electrode of the MOS tube M5 is connected with the external wiring socket 485A.

Preferably, in the RS485 bus protection circuit in the integrated circuit, a source connection point of the MOS transistor M6 is connected to the power supply VCC _3V3 through a pull-up resistor R102; the source connection point of the MOS transistor M5 is connected to the inside through a pull-down resistor R103, so as to increase the feasibility of the signal.

Preferably, in the RS485 bus protection circuit in the integrated circuit, the source connection point of the MOS transistor M6 is connected to the ground through a capacitor C61, and the source connection point of M6 is connected to the ground through a zener diode VD 5; the source connection point of the MOS transistor M5 is connected with the ground through a capacitor C60, and the source connection point of M5 is connected with the ground through a voltage stabilizing diode VD6, so that the stability of signals is improved.

Preferably, in the RS485 bus protection circuit in the integrated circuit, the 485A end of the external connection jack is connected to a resistor R83, a resistor R83 is connected to a resistor R84, the other end of the resistor R84 is connected to the ground, the anode of the diode D15 is connected to a resistor R83, and the cathode of the diode D15 is connected to the base of the transistor T7; the end of the external wiring socket 485B is connected with a resistor R85, a resistor R85 is connected with a resistor R86, the other end of the resistor R86 is connected with the inside, the anode of a diode D16 is connected with R85, and the cathode of a diode D16 is connected with the base of a triode T7.

Preferably, in the RS485 bus protection circuit in the integrated circuit, a collector of the transistor T7 is connected to the line connection identifier PRS485, and an emitter of the transistor T7 is connected to the inside.

In the RS485 bus protection circuit in the integrated circuit, after an external circuit is short-circuited, the voltages of the external connection jack 485A and the external connection jack 485B are also increased and are greater than 6.6V, after each external circuit passes through a voltage dividing resistor, the diode D15 and the diode D16 are turned on, the transistor T7 is turned on, the control circuit connected with the line connection identifier PRS485 is turned on, so that the line connection identifier RS 485G flows into the line connection identifier PRS485, thereby lowering the gate voltage of UG (source voltage of the MOS transistor M5 and the MOS transistor M6), further lowering the gate voltages of the MOS transistor M5 and the MOS transistor M6 and meeting the conditions of UG ≦ US (source voltage of the MOS transistor M5 and the MOS transistor M6), and disconnecting the MOS transistor M5 and the MOS transistor M6 to protect the 485 communication loop and the chip.

Preferably, in the RS485 bus protection circuit in the integrated circuit, a pin RS485 EN of the single chip microcomputer chip N4 is connected with the resistor R89, the resistor R89 is connected with the resistor R90, and the resistor R90 is connected with the inside; the base of the transistor T9 is connected to the resistor R90, the collector of the transistor T9 is connected to the resistor R88, and the emitter of the transistor T9 is connected to the ground.

Preferably, in the RS485 bus protection circuit in the integrated circuit, the 11V voltage input terminal V11PRE is connected to an emitter of the transistor T8, a base of the transistor T8 is connected to the resistor R88, a collector of the transistor is connected to the line connection identifier RS 485G, and the resistor R87 is connected between the emitter and the collector of the transistor T8.

Preferably, in the RS485 bus protection circuit in the integrated circuit, the GND of the power module N1 is isolated from the ground; the IN of the isolation power supply module N1 is connected with the emitter of the triode T17, the anode of the polar capacitor C6 is connected with the emitter of the triode T17, and the other end of the capacitor C6 is connected with the inside; one end of the capacitor C7 is connected with an emitter of the triode T17, and the other end of the capacitor C7 is connected with the ground; one end of the capacitor C8 is connected to the emitter of the transistor T17, and the other end of the capacitor C8 is connected to the ground.

Preferably, in the RS485 bus protection circuit in the integrated circuit, a collector of the transistor T17 is connected to an external circuit UBR; one end of the resistor R14 is connected with the collector of the triode T17, and the other end of the resistor R17 is connected with the anode of the zener diode VD 9; the anode of the voltage-stabilizing diode VD9 is connected with the base electrode of the triode T17, and the cathode of the voltage-stabilizing diode VD9 is connected with the ground; one end of the capacitor C4 is connected to the base of the transistor T17, and the other end of the capacitor C4 is connected to the ground.

Preferably, in the RS485 bus protection circuit in the integrated circuit, the OUT port of the isolation power supply module N1 outputs a stable voltage VCC _3V3 to supply power to the RS485 communication chip N3 and the single chip microcomputer chip N4; one end of the capacitor C9 is connected to VCC _3V3(3.3V regulated voltage), and the other end of the capacitor C9 is connected to ground; one end of the capacitor C10 is connected to VCC _3V3(3.3V regulated voltage), and the other end of the capacitor C10 is connected to the ground.

Preferably, in the RS485 bus protection circuit in the integrated circuit, the ADC _03 detection circuit is formed by connecting one end of a voltage dividing resistor R75 in series between a negative electrode P-of the integrated circuit board and the ground, connecting the other end of a resistor R75 with a voltage dividing resistor R76, and connecting the other end of a resistor R76 with the ground; one end of the resistor R77 is connected with a pin ADC _03 of the singlechip chip N4, and the other end of the resistor R77 is connected with the joint of the resistor R75 and the resistor R76; one end of the capacitor C50 is connected with the junction of the resistor R75 and the resistor R76, and the other end of the capacitor C50 is connected with the ground.

The utility model discloses the structure has following beneficial effect:

the RS485 bus protection circuit in the integrated circuit can effectively prevent short-circuit transient high current from damaging an RS485 communication line, protects the RS485 serial bus, and ensures stable operation of the RS485 serial bus.

Drawings

Fig. 1 is an ADC03 detection circuit of an RS485 bus protection circuit in an integrated circuit according to the present invention;

fig. 2 is a partial pin of the single chip N4 of the RS485 bus protection circuit in the integrated circuit of the present invention;

fig. 3 shows an isolated power supply module N1 and peripheral circuits of the RS485 bus protection circuit in the integrated circuit of the present invention;

fig. 4 shows an RS485 communication chip N3 and peripheral circuits of an RS485 bus protection circuit in the integrated circuit of the present invention;

fig. 5 is a circuit with partial protection function of the RS485 bus protection circuit in the integrated circuit.

Detailed Description

For further explanation of the present invention, reference will now be made in detail to the accompanying drawings:

as shown IN fig. 1-5, an RS485 bus protection circuit IN an integrated circuit includes an isolation power module N1(BL8078CC3TR33), an RS485 communication chip N3(YD3082E), a single chip microcomputer chip N4(STM32F030C8), and an ADC _03 detection circuit, where a GND pin of the isolation power module N1 is connected to the inside, an IN pin of the N1 is connected to an emitter of a triode T17, and an OUT pin of the N1 outputs a stable voltage VCC _3V3 to supply power to the RS485 communication chip N3 and the single chip microcomputer chip N4; UART1_ RX (single chip microcomputer chip N4's pin) is connected to RS485 communication chip N3's 1 foot, RE (single chip microcomputer chip N4's pin) is connected to RS485 communication chip N3's 2 feet, DE (single chip microcomputer chip N4's pin) is connected to RS485 communication chip N3's 3 feet, RS485 communication chip N3's 4 feet are connected and are connect inside ground end UART1_ TX (single chip microcomputer chip N4's pin), RS485 communication chip N3's 5 feet are connected inside ground, RS485 communication chip N3's 6 feet, 7 feet connect outside connection 485A in proper order, outside connection 485B end, RS485 communication chip N3's 8 feet connect 3.3V power, effectively prevent the loop-broken of short circuit transient state high current to RS485 communication line, have guaranteed the steady operation of RS485 serial bus.

Pins

The pin 7 of the RS485 communication chip N3 is connected with a resistor R101; and the pin 8 of the RS485 communication chip N3 is connected with the resistor R102 and used for limiting current. The protection circuit for protecting the RS485 communication chip N3(YD3082E) comprises an MOS tube M5 and an MOS tube M6, wherein the source electrode of the MOS tube M5 is connected with a resistor R101 in series, the grid electrode of the MOS tube M5 is connected with a PRS485 (line connection identifier) and a resistor R106, and the drain electrode of the MOS tube M5 is connected with an external wiring socket 485B; the source electrode of the MOS tube M6 is connected in series with the resistor R102, the grid electrode of the MOS tube M6 is connected with the PRS485 (line connection identifier) and the resistor R106, and the drain electrode of the MOS tube M5 is connected with the external wiring socket 485A.

The source electrode connecting point of the MOS transistor M6 is connected with the power supply VCC _3V3(3.3V stable voltage) through a pull-up resistor R102; the source connection point of the MOS transistor M5 is connected to the ground via a pull-down resistor R103. The source electrode connecting point of the MOS tube M6 is connected with the ground through a capacitor C61, and the source electrode connecting point of M6 is connected with the ground through a voltage stabilizing diode VD 5; the source connection point of the MOS transistor M5 is connected with the ground through a capacitor C60, and the source connection point of M5 is connected with the ground through a voltage stabilizing diode VD 6.

The end A of the external wiring socket 485 is connected with a resistor R83, a resistor R83 is connected with a resistor R84, the other end of the resistor R84 is connected with the inside, the anode of a diode D15 is connected with a resistor R83, and the cathode of a diode D15 is connected with the base electrode of a triode T7; the end of the external wiring socket 485B is connected with a resistor R85, a resistor R85 is connected with a resistor R86, the other end of the resistor R86 is connected with the inside, the anode of a diode D16 is connected with R85, and the cathode of a diode D16 is connected with the base of a triode T7.

The collector of the transistor T7 is connected to PRS485 (line connection indicator), and the emitter of the transistor T7 is connected to the ground. The single chip microcomputer control signal RS485 EN (a pin of the single chip microcomputer chip N4) is connected with the resistor R89, the resistor R89 is connected with the resistor R90, and the resistor R90 is connected with the ground; the base electrode of the triode T9 is connected with the resistor R90, the collector electrode of the triode T9 is connected with the resistor R88, and the emitter electrode of the triode T9 is connected with the ground; the 11V voltage input end V11PRE is connected with an emitting electrode of the triode T8, a base electrode of the triode T8 is connected with the resistor R88, a collector electrode of the triode is connected with the line connection identification RS 485G, and a resistor R87 is connected between the emitting electrode and the collector electrode of the triode T8.

The GND and the grounding of the isolation power supply module N1; the IN of the isolation power supply module N1 is connected with the emitter of the triode T17, the anode of the polar capacitor C6 is connected with the emitter of the triode T17, and the other end of the capacitor C6 is connected with the inside; one end of the capacitor C7 is connected with an emitter of the triode T17, and the other end of the capacitor C7 is connected with the ground; one end of the capacitor C8 is connected with an emitter of the triode T17, and the other end of the capacitor C8 is connected with the ground; the collector of the triode T17 is connected with an external circuit UBR; one end of the resistor R14 is connected with the collector of the triode T17, and the other end of the resistor R17 is connected with the anode of the zener diode VD 9; the anode of the voltage-stabilizing diode VD9 is connected with the base electrode of the triode T17, and the cathode of the voltage-stabilizing diode VD9 is connected with the ground; one end of the capacitor C4 is connected to the base of the transistor T17, and the other end of the capacitor C4 is connected to the ground.

An OUT port of the isolation power supply module N1 outputs a stable voltage VCC _3V3 to supply power to the RS485 communication chip N3 and the singlechip chip N4; one end of the capacitor C9 is connected to VCC _3V3(3.3V regulated voltage), and the other end of the capacitor C9 is connected to ground; one end of the capacitor C10 is connected to VCC _3V3(3.3V regulated voltage), and the other end of the capacitor C10 is connected to the ground.

The ADC _03 detection circuit is characterized in that one end of a voltage dividing resistor R75 connected in series between the negative electrode P-of the integrated circuit board and the ground is connected, the other end of a resistor R75 is connected with a voltage dividing resistor R76, and the other end of a resistor R76 is connected with the ground; one end of the resistor R77 is connected with a pin ADC _03 of the singlechip chip N4, and the other end of the resistor R77 is connected with the joint of the resistor R75 and the resistor R76; one end of the capacitor C50 is connected with the junction of the resistor R75 and the resistor R76, and the other end of the capacitor C50 is connected with the ground.

The working principle of the RS485 bus protection circuit in the integrated circuit is as follows:

the isolation power supply module N1 converts the power supply IN into a 3.3V power supply VCC _3V3(3.3V stable voltage) to be supplied to the RS485 chip U2, and 485 communication works normally. The 2 pins of the RS485 are connected through a pull-down resistor R100, the 3 pins are connected through a pull-down resistor R139, and the pull-down resistors R100 and R139 can control the output direction of the bus. The MOS tubes M5 and M6 are both N-strand type, and are switched on when UG > US and switched off when UG ≦ US. During normal communication, the voltage of the 485A and the 485B is in a normal value range, and after the voltage division effect of the voltage division resistors R83\ R84 and R85\ R86D, the positive electrodes of the diodes D15 and D16 do not reach the conducting voltage of 0.6V, so the triode T7 is not conducted. Further, when the base of the triode T7 is greater than the emitter by 0.7V, the transistor is turned on, and when the potential of the transmitter ground GND of the T7 is 0V, the circuit connected to the PRS485 (line connection identifier) is turned on when the base is greater than 0.7V. When the on voltage of the diode D15 or D16 is 0.6V or more, the potential of the voltage UTP121 or UTP122 at the node TP121 or TP122 becomes 0.6V or more, and according to the series resistance voltage division theorem, if UTP121 ═ R83R83+ R84 · UTP119 becomes higher than 0.6 × 11V, that is, 6.6V, from the voltage UTP119 of 485A. During normal communication, singlechip chip control end RS485 EN outputs high level (fig. 2), triode T8, T9 switch on, and RS 485G (line connection sign) exports a high level for MOS pipe M5, M6, and the control circuit that PRS485 (line connection sign) connects does not switch on, MOS pipe M5, M6 satisfy the condition of switching on, 485 normal communication.

After the external circuit is short-circuited, the circuit current is increased suddenly, the voltage is increased, the voltages of 485A and 485B are also increased (larger than 6.6V), after the external circuit passes through the divider resistor, the diodes D15 and D16 are conducted, the T7 is conducted, a control circuit (shown in figure 5) connected with the PRS485 (line connection identifier) is conducted, and the RS 485G (line connection identifier) flows into the PRS485 (line connection identifier) circuit, so that the UG is reduced, the UG of the MOS tubes M5 and M6 is reduced, and the UG ≦ US condition is met, the MOS tubes M5 and M6 are disconnected, and a 485 communication loop and a chip are protected.

When the P-voltage is increased suddenly, the P-voltage dividing resistors R75 and R77 are connected, so that the ADC03 detects an overvoltage signal, the control port 485EN of the single chip N4 outputs a low level, the base of the triode T9 is controlled to be at the low level, the collector of the triode T9 is at the low level, the base of the triode T8 is controlled to be at the low level, the emitter of the triode T8 outputs low, namely the output of the RS 485G (line connection identifier) is low, UG of the MOS tubes M5 and M6 controlled by the RS 485G (line connection identifier) is reduced and meets the condition that UG is less than or equal to US, the MOS tubes M5 and M6 are disconnected, and a 485 communication loop and a chip are protected.

Furthermore, after short-circuit protection is carried out, the R485 circuit is controlled to be closed by the single chip microcomputer, after the fault is eliminated, the RS485 is wakened up by outputting a high level through the single chip microcomputer control port 485AIO, and a wakening signal is sent to the 485A through the diode D18 to enable the 485A to work normally.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. The utility model provides a RS485 bus protection circuit among integrated circuit which characterized in that: the detection circuit comprises an isolation power supply module N1, an RS485 communication chip N3, a single chip microcomputer chip N4 and an ADC _03 detection circuit, wherein a GND pin of the isolation power supply module N1 is connected with the ground, an IN pin of the N1 is connected with an emitter of a triode T17, and an OUT pin of the N1 outputs a stable voltage VCC _3V3 to supply power to the RS485 communication chip N3 and the single chip microcomputer chip N4; a pin 1 of the RS485 communication chip N3 is connected with a pin UART1_ RX of a singlechip chip N4, a pin 2 of the RS485 communication chip N3 is connected with a pin RE of the singlechip chip N4, a pin 3 of the RS485 communication chip N3 is connected with a pin DE of the singlechip chip N4, a pin 4 of the RS485 communication chip N3 is connected with a pin UART1_ TX of the singlechip chip N4 at the end connected with the ground, a pin 5 of the RS485 communication chip N3 is connected with the ground, a pin 6 and a pin 7 of the RS485 communication chip N3 are sequentially connected with an external wiring socket 485A and an external wiring socket 485B end, and a pin 8 of the RS485 communication chip N3 is connected with 3.3V output by an isolation power supply module N1; pins 1, 9, 24 and 48 of the singlechip chip N4 are all pulled up to 3.3V for power supply and are connected with the ground through capacitors C53, C57, C58 and C52; for the sake of clarity of connection, 17 pins of ADC _ IN7 are coded as ADC03, 30 pins are coded as UART1_ TX, 31 pins are coded as UART1_ RX, 33 pins of I/O ports are coded as RE, 35 pins of I/O ports are coded as RS485_ EN, and 36 pins of I/O ports are coded as DE; the ADC _03 detection circuit adopts a voltage value at the negative pole of the integrated circuit in a series resistance voltage division mode and transmits the voltage value to an ADC03 pin of the single chip microcomputer chip N4.

2. The RS485 bus protection circuit of claim 1, wherein: the pin 7 of the RS485 communication chip N3 is connected with a resistor R101; and the pin 8 of the RS485 communication chip N3 is connected with the resistor R102.

3. The RS485 bus protection circuit of claim 2, wherein: the circuit also comprises an MOS tube M5 and an MOS tube M6, wherein the source electrode of the MOS tube M5 is connected with a resistor R101 in series, the grid electrode of the MOS tube M5 is connected with a control end circuit connection identifier PRS485 and a resistor R106, and the drain electrode of the MOS tube M5 is connected with an external wiring socket 485B; the source electrode of the MOS tube M6 is connected with the resistor R102 in series, the grid electrode of the MOS tube M6 is connected with the control end line connection mark PRS485 and the resistor R106, and the drain electrode of the MOS tube M5 is connected with the external wiring socket 485A.

4. The RS485 bus protection circuit of claim 3, wherein: the source electrode connecting point of the MOS tube M6 is connected with the ground through a capacitor C61, and the source electrode connecting point of M6 is connected with the ground through a voltage stabilizing diode VD 5; the source connection point of the MOS transistor M5 is connected with the ground through a capacitor C60, and the source connection point of M5 is connected with the ground through a voltage stabilizing diode VD6, so that the stability of signals is improved.

5. The RS485 bus protection circuit of claim 1, wherein: the end A of the external wiring socket 485 is connected with a resistor R83, a resistor R83 is connected with a resistor R84, the other end of the resistor R84 is connected with the inside, the anode of a diode D15 is connected with a resistor R83, and the cathode of a diode D15 is connected with the base electrode of a triode T7; the end of the external wiring socket 485B is connected with a resistor R85, a resistor R85 is connected with a resistor R86, the other end of the resistor R86 is connected with the inside, the anode of a diode D16 is connected with R85, and the cathode of a diode D16 is connected with the base of a triode T7.

6. The RS485 bus protection circuit of claim 1, wherein: the pin RS485 EN of the singlechip chip N4 is connected with a resistor R89, a resistor R89 is connected with a resistor R90, and the resistor R90 is connected with the inside; the base of the transistor T9 is connected to the resistor R90, the collector of the transistor T9 is connected to the resistor R88, and the emitter of the transistor T9 is connected to the ground.

7. The RS485 bus protection circuit of claim 1, wherein: the GND and the grounding of the isolation power supply module N1; the IN of the isolation power supply module N1 is connected with the emitter of the triode T17, the anode of the polar capacitor C6 is connected with the emitter of the triode T17, and the other end of the capacitor C6 is connected with the inside; one end of the capacitor C7 is connected with an emitter of the triode T17, and the other end of the capacitor C7 is connected with the ground; one end of the capacitor C8 is connected to the emitter of the transistor T17, and the other end of the capacitor C8 is connected to the ground.

8. The RS485 bus protection circuit of claim 1, wherein: an OUT port of the isolation power supply module N1 outputs a stable voltage VCC _3V3 to supply power to the RS485 communication chip N3 and the singlechip chip N4; one end of the capacitor C9 is connected with VCC _3V3, and the other end of the capacitor C9 is connected with the ground; one end of the capacitor C10 is connected to VCC _3V3, and the other end of the capacitor C10 is connected to the ground.

9. The RS485 bus protection circuit of claim 1, wherein: the ADC _03 detection circuit is characterized in that one end of a voltage dividing resistor R75 connected in series between the negative electrode P-of the integrated circuit board and the ground is connected, the other end of a resistor R75 is connected with a voltage dividing resistor R76, and the other end of a resistor R76 is connected with the ground; one end of the resistor R77 is connected with a pin ADC _03 of the singlechip chip N4, and the other end of the resistor R77 is connected with the joint of the resistor R75 and the resistor R76; one end of the capacitor C50 is connected with the junction of the resistor R75 and the resistor R76, and the other end of the capacitor C50 is connected with the ground.