CN200950538Y - RS-485 Communication interface protective circuit - Google Patents
RS-485 Communication interface protective circuit Download PDFInfo
- Publication number
- CN200950538Y CN200950538Y CN 200620052388 CN200620052388U CN200950538Y CN 200950538 Y CN200950538 Y CN 200950538Y CN 200620052388 CN200620052388 CN 200620052388 CN 200620052388 U CN200620052388 U CN 200620052388U CN 200950538 Y CN200950538 Y CN 200950538Y
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- communication interface
- circuit
- voltage
- protective circuit
- utility
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Abstract
The utility model discloses a RS-485 communication interface protection circuit, which comprises a voltage-dependent resistor connected in series with a data cable A of the RS-485 communication interface and another voltage-dependent resistor connected in series with a data cable B of the RS-485 communication interface, a transient voltage suppressor connected in parallel between the data cable A and the data cable B, a voltage stabilizing diode connected in parallel between the cable A and the ground and a voltage stabilizing diode connected in parallel between the cable B and the ground. The transient voltage suppressor of the utility model can protect the circuit before the thermosentitive resistance plays the role in providing a circuit for transient current to protect the circuit, which make the communication circuit can not be stricken due to overvoltage or be destroyed due to overcurrent.
Description
Technical field
The utility model relates to a kind of RS-485 communication interface protective circuit.
Background technology
The RS-485 standard is often used as to a kind of relatively economical, have that suitable strong noise suppresses, the communications platform of high relatively transmission rate, long transmission distance, wide common mode range.Simultaneously, the RS-485 circuit has control advantage such as convenient, with low cost.RS-485 is widely used as data transmission link in electric energy meter centralized automatic meter-reading field as a kind of electrical code of multiple spot differential data transmission.
The RS-485 communication interface is used a pair of twisted-pair feeder, and wherein a line is defined as A, and another line is defined as B.Transmitting and Receiving End is corresponding with B-B continuous with A-A by the balancing twisted-pair line.When the level that between receiving terminal A-B, has greater than+200mV, be output as the positive logic level; During less than-200mV, be output as the negative logic level.On the receiving balance line of receiver transmitter, level range is usually between 200mV to 6V.
Though effective esd protection measure that RS-485 communication chip itself is integrated, but the RS-485 interface is when networking is connected up and in service in system, and the high pressure that the RS-485 bus may be produced by external interference (thunderbolt, surge, static) damages the RS-485 port; And certain customers' attempt in use makes the electric energy meter operation irregularity, thereby reaches the purpose of stealing by malicious sabotage, attack RS-485 telecommunication cable.Therefore the RS-485 communication interface also is provided with external protective circuit as shown in Figure 1, D7～D8 in the circuit diagram, and D11 and RTC1, RTC2 are the protection components and parts, its effect is as follows: insert two diode 1N4007 (D7～D10), play clamper respectively at A and B end.When the voltage of input is higher than the V485+0.7 volt, clamp the voltage at the V485+0.7 volt; When the voltage of input is lower than the G485-0.7 volt, clamp the voltage at the G485-0.7 volt.Prevent the RS-485 communication chip and damage because of the high voltage input.The Transient Voltage Suppressor TVS pipe in parallel at RS-485 voltage two ends (P6KE6.8CA, D11), when transient voltage surpasses the normal working voltage of circuit; diode generation snowslide; for transient current provides path, protection RS-485 part power supply is used for electrostatic discharge (ESD) protection.Serial connection 20 Ω thermistor RTC1, RTC2 in A and B circuit.When A and B termination are gone into high voltage, thermistor will generate heat because of the increase of electric current, and the resistance of thermistor also will increase, thereby guarantee that the chip input is not damaged by high pressure.
Above-mentioned protective circuit in most of the cases makes the RS-485 interface obtain better must the protection, but discovery is not too perfect in actual use, still often has the impaired situation of RS-485 interface to take place, and brings very big inconvenience for user's life
The utility model content
For solving the existing existing problem of RS-485 communication interface circuit, the utility model provides a kind of simple in structure, safe and reliable RS-485 communication interface protective circuit.
The technical scheme that the utility model solves the problems of the technologies described above is: comprise the piezo-resistance that is serially connected with respectively on RS-485 communication interface A, the B data wire, connect voltage stabilizing didoe respectively between A, B data wire and the ground.
In the above-mentioned RS-485 communication interface protective circuit, between described A, the B data wire and connect Transient Voltage Suppressor.
The beneficial effects of the utility model: 1) in the utility model Transient Voltage Suppressor is attempted by between A, the B data wire; when extraneous high pressure is added in A, the B end police; because the hot operate time of protection of thermistor needs 2～3 seconds; when thermistor does not also play a protective role; Transient Voltage Suppressor will play the effect of protection earlier; for transient current provides path, make telecommunication circuit can not puncture because of overvoltage or exceed the quata electric current and overheated burning.2) use 4 diodes of protective circuit instead 2 voltage stabilizing didoes in the utility model, both played the effect of clamper, reduced components and parts simultaneously and saved material cost.
Below in conjunction with the drawings and specific embodiments the utility model is further described.
Description of drawings
Fig. 1 is the protective circuit figure of existing RS-485 communication interface.
Fig. 2 electrical schematic diagram of the present utility model.
Embodiment
With reference to Fig. 1, Fig. 1 is an electrical schematic diagram of the present utility model.Zener diode D5, D6 among the figure, Transient Voltage Suppressor TVS1 and thermistor RT1, RT2 are the circuit protection components and parts.Transient Voltage Suppressor is connected in parallel on A, B end behind the thermistor.When the external world applies high voltage such as 220VAC at A, B end, because the hot operate time of protection of thermistor needs 2～3 seconds, when thermistor did not also play a protective role, Transient Voltage Suppressor will play the effect of protection earlier.Because of the response time of Transient Voltage Suppressor is lacked (about 1ns) very much, when thermistor does not also move, Transient Voltage Suppressor generation snowslide for transient current provides path, makes telecommunication circuit can not puncture because of overvoltage or exceed the quata electric current and overheated burning.After 2～3 seconds after Transient Voltage Suppressor plays protection to do usefulness; increasing because of the electric current overrate of thermistor; thereby the Transient Voltage Suppressor both end voltage reduces, and the high pressure drop that the external world is applied drops on the thermistor, has guaranteed the safety of communication interface inside.
The RS-485 communication interface of electric energy meter has used the circuit after improving carrying out direct discharge test of 8KV static and 380VAC forceful electric power pressure challenge trial 4 hours, and after other tests, communication interface all stands intact.
Claims (2)
1, a kind of RS-485 communication interface protective circuit comprises the piezo-resistance that is serially connected with respectively on RS-485 communication interface A, the B data wire, it is characterized in that: between A, B data wire and the ground respectively and connect voltage stabilizing didoe.
2, RS-485 communication interface protective circuit according to claim 1 is characterized in that: between A, the B data wire and connect Transient Voltage Suppressor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200620052388 CN200950538Y (en) | 2006-09-30 | 2006-09-30 | RS-485 Communication interface protective circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200620052388 CN200950538Y (en) | 2006-09-30 | 2006-09-30 | RS-485 Communication interface protective circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN200950538Y true CN200950538Y (en) | 2007-09-19 |
Family
ID=38893080
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 200620052388 Expired - Lifetime CN200950538Y (en) | 2006-09-30 | 2006-09-30 | RS-485 Communication interface protective circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN200950538Y (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101938119A (en) * | 2009-06-30 | 2011-01-05 | 万国半导体股份有限公司 | Transient voltage suppressor (TVS) with improved clamping voltage |
| CN101989740A (en) * | 2010-08-06 | 2011-03-23 | 许晓华 | Analogue interface protecting circuit |
| CN102722926A (en) * | 2012-05-30 | 2012-10-10 | 深圳光启创新技术有限公司 | Photon client |
| CN103066581A (en) * | 2011-10-19 | 2013-04-24 | 北京谊安医疗***股份有限公司 | Medical air supply system and electrostatic protection circuit of communication circuit thereof |
| CN105740183A (en) * | 2016-01-25 | 2016-07-06 | 上海斐讯数据通信技术有限公司 | Serial port communication circuit |
-
2006
- 2006-09-30 CN CN 200620052388 patent/CN200950538Y/en not_active Expired - Lifetime
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101938119A (en) * | 2009-06-30 | 2011-01-05 | 万国半导体股份有限公司 | Transient voltage suppressor (TVS) with improved clamping voltage |
| CN101989740A (en) * | 2010-08-06 | 2011-03-23 | 许晓华 | Analogue interface protecting circuit |
| CN103066581A (en) * | 2011-10-19 | 2013-04-24 | 北京谊安医疗***股份有限公司 | Medical air supply system and electrostatic protection circuit of communication circuit thereof |
| CN102722926A (en) * | 2012-05-30 | 2012-10-10 | 深圳光启创新技术有限公司 | Photon client |
| CN105740183A (en) * | 2016-01-25 | 2016-07-06 | 上海斐讯数据通信技术有限公司 | Serial port communication circuit |
| CN105740183B (en) * | 2016-01-25 | 2018-05-18 | 上海斐讯数据通信技术有限公司 | Serial port communication circuit |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| C56 | Change in the name or address of the patentee |
Owner name: CHINA ELECTRIC HUNAN WEIKE ELECTRIC POWER METER CO Free format text: FORMER NAME: HUNAN WEIKE ELECTRIC POWER METER CO., LTD. |
|
| CP03 | Change of name, title or address |
Address after: Block M14, building B, hi tech Industrial Development Zone, silver basin South Road, Hunan, Changsha, 410013 Patentee after: Hunan Zhongdian Weike Electric Meter Co., Ltd. Address before: 352, Jia Jia Hu Road, Yuelu District, Hunan, Changsha: 410013 Patentee before: Hunan Weike Power Meter Co., Ltd. |
|
| C56 | Change in the name or address of the patentee |
Owner name: HUNAN WILLFAR INFORMATION TECHNOLOGY CO., LTD. Free format text: FORMER NAME: HUNAN ZHONGDIAN WEIKE ELECTRIC METER CO., LTD. |
|
| CP01 | Change in the name or title of a patent holder |
Address after: 410013. B building, M14 building, hi tech Industrial Development Zone, silver basin South Road, Hunan, Changsha Patentee after: Hunan Weike Power Meter Co., Ltd. Address before: 410013. B building, M14 building, hi tech Industrial Development Zone, silver basin South Road, Hunan, Changsha Patentee before: Hunan Zhongdian Weike Electric Meter Co., Ltd. |
|
| CX01 | Expiry of patent term |
Granted publication date: 20070919 |
|
| EXPY | Termination of patent right or utility model |