CN201466706U

CN201466706U - Anti-lightning protection circuit of RS485 serial communication interface

Info

Publication number: CN201466706U
Application number: CN2009200735568U
Authority: CN
Inventors: 夏青
Original assignee: SHANGHAI ZHENHE LIGHTNINGPROOF ELECTRIC TECHNOLOGY Co Ltd
Current assignee: SHANGHAI ZHENHE LIGHTNINGPROOF ELECTRIC TECHNOLOGY Co Ltd
Priority date: 2009-06-09
Filing date: 2009-06-09
Publication date: 2010-05-12
Anticipated expiration: 2019-06-09

Abstract

The utility model relates to an anti-lightning protection circuit of an RS485 serial communication interface, which comprises a full-duplex network and is characterized in that the anti-lightning protection circuit achieves the same anti-lightning effect on equal signal wires of the signal ground at the RS485 communication interface and adopts a two-stage compound anti-lightning structure, that is, a gas-discharge tube is adopted at the input port for primary anti-lightning and a full-bridge rectifying and a transient voltage are adopted to restraint a diode at the output port for secondary lightning protection, and wirewound non-inductive resistor are connected in series between the two stages of anti-lightning as the ignition resistor of the gas-discharge tube in the primary stage and the current-limiting resistor of the secondary anti-lightning. By adopting the anti-lightning protection circuit, the main energy of lightning stroke can be discharged in case of a lightning stroke.

Description

The lightning protection circuit of RS485 serial communication interface

Technical field

The utility model relates to a kind of lightning protection circuit of RS485 serial communication interface, belongs to the lightning-protection engineering field.

Technical background

Along with the development of digital communication and popularizing of intelligent appliance, the RS485 interface has been widely used in numerous areas such as Industry Control, instrument, instrument, multi-media network, electromechanical integrated product.A system often is made up of the terminal of the mutual communication of a plurality of needs.For example, all there are the problem of multistation, telecommunication in the Automatic meter reading system of building safety supervisory control system, gas meter, water power table, the automatic fare collection system in supermarket etc.Require communication distance be tens meters on during km because the RS485 bus only needs three lines can realize that the multistation networking constitutes distributed system, equipment is simple, cheap, and transfer rate is up to 10MHz, so obtain extensive use in engineering project.

When constituting the RS485 bus network, because the network topology of RS485 adopts the bus type structure of terminal coupling, promptly logical bus is connected in series each node, do not support annular or Star Network, therefore, the moment that thunder and lightning causes often causes a plurality of RS485 transceivers on the transmission line to damage, so problem that must consideration in lightning protection measures actual use that be the RS485 technology also is crucial measure of raising system reliability.

But a kind of wrong viewpoint is thought RS485 communication link undesired signal ground exactly, and just uses a pair of twisted-pair feeder that " A ", " B " end of each interface are coupled together simply.Therefore, RS485 lightning Protection Design both domestic and external, or not signal ground is carried out lightning protection, otherwise it is excessive just just signal ground to be done lightning protection as a screen.This makes the lightning protection of RS485 equal illusory.

Fig. 1 is typical R S485 half-duplex network figure, and Fig. 2 is typical R S485 full duplex network figure.Can see that from Fig. 1, Fig. 2 signal ground exists electrical potential difference with protection ground, if signal ground is not carried out lightning protection, must damage the RS485 drive circuit during thunderbolt.

Fig. 3 adopts such lightning protection device for traditional RS485 lightning protection circuit that does not have signal ground, and when signal ground was struck by lightning, the RS485 network was with badly damaged.Fig. 4 is the RS485 lightning protection circuit that tradition has signal ground, owing to do not have current limliting and TVS clamp on the signal ground GND circuit, can't protect equally during thunderbolt, and the RS485 network is with badly damaged.

Summary of the invention

The purpose of this utility model is to propose the lightning protection circuit of RS485 serial communication interface; this lightning protection circuit; adopt the compound lightning protection structure of two-stage; when thunderbolt produces; produce surge no matter be at holding wire A, B or on signal ground GND; at first electric current is through current-limiting resistance R1, R2 or R3, and the three-phase bridge rectification circuit of forming through D1～D6 is suppressed diode with voltage clamp by transient voltage then.To raise the voltage of A, B or GND end, impel gas discharge tube G1, G2 or G3 igniting conducting, thereby make main energy earial drainage from first order lightning protection of thunderbolt.

For achieving the above object; the technical solution of the utility model is; protective circuit adopts the compound lightning protection structure of two-stage, and input port adopts gas discharge tube as first order lightning protection, and output port adopts full-bridge rectification to add type transient voltage inhibition diode as second level lightning protection.Seal in the wire-wound noninductive resistance between the two-stage lightning protection as the gas discharge tube igniting resistance of the first order and the current-limiting resistance of second level lightning protection.

Circuit analysis is an example with figure five.When thunderbolt produced, no matter be to produce surge at holding wire A, B or on signal ground GND, at first electric current was through current-limiting resistance R1, R2 or R3, and the three-phase bridge rectification circuit of forming through D1～D6 is suppressed diode with voltage clamp by transient voltage then.TVS1 guarantees not produce high pressure between holding wire A ', B ', the signal ground GND ', and TVS2, TVS3 guarantee that holding wire A ', B ' and signal ground GND ' do not produce high pressure to PE safely.Simultaneously, when current flowing resistance R1, R2 or R3, will raise the voltage of A, B or GND end, impel gas discharge tube G1, G2 or G3 igniting conducting, thereby make main energy earial drainage from first order lightning protection of thunderbolt.

The beneficial effects of the utility model adopt such lightning protection device, and when signal ground was struck by lightning, the RS485 network was with badly damaged.Fig. 4 is the RS485 lightning protection circuit that tradition has signal ground, owing to do not have current limliting and TVS clamp on the signal ground GND circuit, can't protect equally during thunderbolt, and the RS485 network is with badly damaged.

Below in conjunction with drawings and Examples to the utility model detailed explanation of making comparisons.

Description of drawings

Fig. 1 is a typical R S485 half-duplex network schematic diagram;

Fig. 2 is a typical R S485 full duplex network schematic diagram;

Fig. 3 does not have the RS485 lightning protection circuit of signal ground for tradition;

Fig. 4 has the RS485 lightning protection circuit of signal ground for tradition;

Fig. 5 is equal to lightning protection circuit for half-duplex RS 485 signal grounds of the present utility model and signal;

Fig. 6 is equal to lightning protection circuit for full duplex RS485 signal ground of the present utility model and signal.

Embodiment

With reference to Fig. 1, Fig. 2, Fig. 1 is typical R S485 half-duplex network figure for a kind of lightning protection circuit of RS485 serial communication interface, and Fig. 2 is typical R S485 full duplex network figure.Can see that from Fig. 1, Fig. 2 signal ground exists electrical potential difference with protection ground, if signal ground is not carried out lightning protection, must damage the RS485 drive circuit during thunderbolt.

With reference to Fig. 3, Fig. 4, Fig. 3 adopts such lightning protection device for traditional RS485 lightning protection circuit that does not have signal ground, and when signal ground was struck by lightning, the RS485 network was with badly damaged.Fig. 4 is the RS485 lightning protection circuit that tradition has signal ground, owing to do not have current limliting and TVS clamp on the signal ground GND circuit, can't protect equally during thunderbolt, and the RS485 network is with badly damaged.

More than be several lightning protection circuits of prior art.

With reference to Fig. 5, Fig. 6, Fig. 5 are equal to lightning protection circuit for half-duplex RS 485 signal grounds of the present utility model and signal; When thunderbolt produced, no matter be to produce surge at holding wire A, B or on signal ground GND, at first electric current was through current-limiting resistance R1, R2 or R3, and the three-phase bridge rectification circuit of forming through D1～D6 is suppressed diode with voltage clamp by transient voltage then.TVS1 guarantees not produce high pressure between holding wire A ', B ', the signal ground GND ', and TVS2, TVS3 guarantee that holding wire A ', B ' and signal ground GND ' do not produce high pressure to PE safely.Simultaneously, when current flowing resistance R1, R2 or R3, will raise the voltage of A, B or GND end, impel gas discharge tube G1, G2 or G3 igniting conducting, thereby make main energy earial drainage from first order lightning protection of thunderbolt.

Though the utility model is described with reference to the above embodiments; but those of ordinary skill in the art; will be appreciated that above embodiment is used for illustrating the utility model; should understand and wherein can make variations and modifications and do not break away from the utility model in a broad sense; so be not that conduct is to qualification of the present utility model; as long as in connotation scope of the present utility model, to the variation of above-described embodiment, the protection range that distortion all will fall into the utility model claim

Claims

1. the lightning protection circuit of a RS485 serial communication interface; comprise full duplex network; it is characterized in that: described lightning protection circuit; the signal ground equivalent signal line of RS485 communication interface is done identical lightning protection; it adopts the compound lightning protection structure of two-stage; promptly adopt gas discharge tube as first order lightning protection by input port; output port adopts full-bridge rectification to add transient voltage inhibition diode as second level lightning protection, seals in the wire-wound noninductive resistance between the two-stage lightning protection as the gas discharge tube igniting resistance of the first order and the current-limiting resistance of second level lightning protection.

2. the lightning protection circuit of serial communication interface as claimed in claim 1 is characterized in that: described second level lightning protection, and the three-phase bridge rectification circuit of forming by D1～D6, and transient voltage suppresses diode and forms.