Protection circuit for communication interface

Abstract

The invention provides a protection circuit of a communication interface. The circuit includes: a first-level protection circuit, a second-level protection circuit and a third-level protection circuit connected in sequence, wherein: the first-level protection circuit includes a current discharge circuit, wherein the current discharge circuit It includes three connection ends, the first connection end is connected to the first signal line of the two signal lines of the RS-485 port, the second connection end is connected to the second signal line of the two signal lines of the RS-485 port, The third connection terminal is connected to the protective ground; the second-level protection circuit includes a first current-limiting resistor, a second current-limiting resistor and a bidirectional transient suppression diode; the third-level protection circuit includes a voltage discharge circuit, wherein the voltage discharge The amplifier circuit is connected to the communication ground, and one end is connected to the two signal lines of the RS‑485 port, and the other end is connected to the RS‑485 transceiver.

Description

technical field [0001] The invention relates to the field of electronic circuits, in particular to a protection circuit for a communication interface. Background technique [0002] As a traditional industrial communication bus, RS-485 adopts balanced transmission and differential reception, has strong ability to suppress common mode interference, has a long transmission distance, can be used for multi-point interconnection, and has low cost. It is widely used in various industrial control sites. Due to the harsh environment of industrial sites, RS-485 ports generally have protection circuits to protect equipment from lightning strikes, surges, and static electricity. [0003] In the existing protection circuits of RS-485 ports, according to the actual application, most of them use current limiting devices and transient suppression diodes for simple anti-surge and anti-static level processing, and the protection ability is relatively weak. There are also some that use the tw...

AI Technical Summary

Problems solved by technology

[0004] In practical applications, due to the difference in the grounding environment of the on-site protective ground, there is a pressure difference between the protective ground and the actual ground. This kind of strong protective structure circuit may not be able to effectively suppress lightning strikes, surges, etc., and the subsequent signal line The breakdown voltage of the transient suppression diode to ground is very low, generally only a few volts, and it is easy to cause breakdown of the protective ground voltage, thus damaging the RS-485 communication port

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