CN108737237A

CN108737237A - A kind of RS485 bus communication circuits based on transformer

Info

Publication number: CN108737237A
Application number: CN201810679383.8A
Authority: CN
Inventors: 谢周悦
Original assignee: ZHEJIANG HECHUAN TECHNOLOGY CO LTD
Current assignee: ZHEJIANG HECHUAN TECHNOLOGY CO LTD
Priority date: 2018-06-27
Filing date: 2018-06-27
Publication date: 2018-11-02

Abstract

The present invention relates to a kind of RS485 bus communication circuits based on transformer, the circuit is with CN1, CN2 is network interface connector, RS485 signals pass through the 3rd foot of network interface, 6 feet, signal in bus is connected to primary terminal the 1st through cable, 2 feet, signal is transferred to secondary side through transformer, the 3rd foot of transformer is connected to the 1st foot of common mode inductance and the 2nd feet of D1, the 4th foot of transformer is connected to the 2nd foot of common mode inductance and the 1st feet of D1, the 3rd feet of D1 are connected to GND, Circuit Fault on Secondary Transformer, which powers up GND, holds C1 and C2, signal reaches U1 the 7th after common mode inductance filters, 8 feet, the 8th feet of U1 are connected to Vcc, and C3 is held in power-up over the ground, U1 the 2nd, 5 feet are connected to GND, U1 the 1st, 3, 4 feet are connected to MCU.Take the present invention, improve anti-interference ability, preferably solve the technical barrier of bus type RS485 isolator design complexity, have the characteristics that it is compatible, simple and practical, should be readily appreciated that and control, service life is long and design cost is low.

Description

A kind of RS485 bus communication circuits based on transformer

Technical field

The present invention relates to a kind of RS485 bus communication circuits based on transformer.

Background technology

RS485 is a kind of serial communication interface of low rate, extensively using extensively and industrial circle, supports point-to-points thirty Duplex data communication, receiving and transmitting signal timesharing occupy same bus (twisted-pair feeder).To avoid bus collision, A, B line are by core when 0 level Piece output end really drives, and makes the V of UB-UA=5；And when 1 level or high resistant, A, B line is presented in bus empty used time, chip output Change and biased by outer connecting resistance, and UA is made to be slightly larger than UB.Usually there is larger earth potential difference in teledata connection, be consequently formed Error code or hardware damage are often caused when common mode interference is excessive or under strong interference environment.Currently, in order to improve anti-interference ability, Generally use isolation RS 485 scheme has following two modes, first, being individually insulated T (transmission) signal using optocoupler, R (connects Receive) signal, RE, DE（Selection）, this mode is circuit complexity, and compares other isolation schemes, light-coupled isolation scheme power consumption The cost of maximum, photo-coupler technology can be increased substantially as data rate improves, and manufacture complexity also can be with device Quantity increases and improves, and optocoupler can have the life problems of ageing failure, and circuit diagram is referring to Fig. 1；Second is that directly using RS485 isolating chips, but because integrated chip solution alternative is not high at this stage, cause purchase cost higher, and each family Integrated chip can not be compatible with, and later product batch may have that the friendship phase is longer and expects without substituting, and cause product flexible Property it is insufficient, circuit diagram is referring to Fig. 2.

Invention content

The purpose of the present invention is being directed to above-mentioned deficiency, using pulse transformer isolation method, provide a kind of based on transformation The RS485 bus communication circuits of device.

The technical solution adopted by the present invention is that：A kind of RS485 bus communication circuits based on transformer, it is characterised in that with CN1, CN2 are standard network interface connector, and RS485 signals A, B pass through the 3rd foot of network interface and the 6th foot, the signal warp on two-wire bus Cross that cable is connected to the 1st foot of pulse transformer primary terminal and the 2nd foot, signal are transferred to secondary side after pulse transformer, The 3rd foot of pulse transformer is connected to the 1st foot of common mode inductance and the 2nd foot of D1, and the 4th foot of pulse transformer is connected to common mode electricity 3rd foot of the 1st foot of the 2nd foot and D1 of sense, D1 is connected to GND, and pulse transformer secondary side, which powers up GND, holds C1 and C2, letter The 7th foot and the 8th foot of U1 are reached number after common mode inductance filters, the 8th foot of U1 is connected to Vcc, and C3 is held in power-up over the ground, U1's 2nd foot and the 5th foot are connected to GND, and the 1st foot, the 3rd foot and the 4th foot of U1 are connected to MCU, finally realize RS485 communication every From；Wherein pulse transformer is isolated for node；TVS pipe back clamping is in 5V, for protecting the RS485 inside bus to communicate core Piece, forward direction by voltage clamp in 0.7 V, when for maintaining high level and when bus free in bus between other RS485 chips A, B Required newest bias voltage, and make other absorption pulse transformer rings.

The present invention is taken, is isolated using pulse transformer, anti-interference ability is not only increased, preferably solves bus type The technical barrier of RS485 isolator design complexity, and without be provided separately isolated power supply can signal isolation, without considering number According to flow direction, and baud rate is adaptive in limited range, have the characteristics that it is compatible, simple and practical, should be readily appreciated that and control, simultaneously The service life is longer compared to other products for transformer, and design cost is low.

Description of the drawings

Fig. 1 is a kind of one of the circuit diagram of isolation RS 485 scheme in the prior art.

Fig. 2 is the two of the circuit diagram of a kind of isolation RS 485 scheme in the prior art.

Fig. 3 is the circuit diagram of the present invention.

Specific implementation mode

With reference to specific embodiment, the invention will be further described.

Referring to Fig.1, at this in RS485 bus communication circuits based on transformer, using CN1, CN2 as standard network interface connection Device, RS485 signals A, B pass through the 3rd foot of network interface and the 6th foot, and the signal on two-wire bus is connected to pulse transforming by cable The 1st foot of device primary terminals and the 2nd foot, signal are transferred to secondary side after pulse transformer, and the 3rd foot of pulse transformer is connected to 4th foot of the 1st foot of common mode inductance and the 2nd foot of D1, pulse transformer is connected to the 2nd foot of common mode inductance and the 1st foot of D1, The 3rd foot of D1 is connected to GND, and pulse transformer secondary side, which powers up GND, holds C1 and C2, and signal arrives after common mode inductance filters Up to the 7th foot of U1 and the 8th foot, the 8th foot of U1 is connected to Vcc, and C3 is held in power-up over the ground, and the 2nd foot of U1 and the 5th foot are connected to GND, The 1st foot, the 3rd foot and the 4th foot of U1 is connected to MCU, finally realizes the isolation of RS485 communications；Wherein pulse transformer is for saving Point isolation；TVS pipe back clamping is in 5V, and for protecting the RS485 communication chips inside bus, forward direction is by voltage clamp in 0.7 V, newest bias voltage required between other RS485 chips A, B in bus when for maintaining high level and when bus free, and make Other absorption pulse transformer rings.

Claims

1. a kind of RS485 bus communication circuits based on transformer, it is characterised in that using CN1, CN2 as standard network interface connector, RS485 signals A, B pass through the 3rd foot of network interface and the 6th foot, at the beginning of the signal on two-wire bus is connected to pulse transformer by cable Grade the 1st foot of terminal and the 2nd foot, signal are transferred to secondary side after pulse transformer, and the 3rd foot of pulse transformer is connected to common mode 4th foot of the 1st foot of inductance and the 2nd foot of D1, pulse transformer is connected to the 2nd foot of common mode inductance and the 1st foot of D1, D1's 3rd foot is connected to GND, and pulse transformer secondary side, which powers up GND, holds C1 and C2, and signal reaches U1 after common mode inductance filters The 7th foot and the 8th foot, the 8th foot of U1 is connected to Vcc, and C3 is held in power-up over the ground, and the 2nd foot of U1 and the 5th foot are connected to GND, U1's 1st foot, the 3rd foot and the 4th foot are connected to MCU, finally realize the isolation of RS485 communications；Wherein pulse transformer for node every From；TVS pipe back clamping is in 5V, for protecting the RS485 communication chips inside bus, forward direction in 0.7 V, to use voltage clamp Newest bias voltage required between other RS485 chips A, B in bus when maintaining high level and when bus free, and make other Absorb pulse transformer ring.