CN206533129U - A kind of lightning protection circuit for electronic equipment RS485 interfaces - Google Patents
A kind of lightning protection circuit for electronic equipment RS485 interfaces Download PDFInfo
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- CN206533129U CN206533129U CN201720248410.7U CN201720248410U CN206533129U CN 206533129 U CN206533129 U CN 206533129U CN 201720248410 U CN201720248410 U CN 201720248410U CN 206533129 U CN206533129 U CN 206533129U
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Abstract
The utility model discloses a kind of lightning protection circuit for electronic equipment RS485 interfaces; including first order lightning protection circuit and second level lightning protection circuit; first order lightning protection circuit includes the first ceramic gas discharge tube and the second ceramic gas discharge tube in parallel; the common-mode voltage that the receiving terminal positive pole and negative pole of RS485 interfaces are produced is discharged over the ground by the first ceramic gas discharge tube, and the differential mode voltage that receiving terminal positive pole and negative pole are produced is discharged by the second ceramic gas discharge tube；Current-limiting resistance that the high current that second level lightning protection circuit includes suppressing the output of first order lightning protection circuit passes through and the output residual voltage of first order lightning protection circuit is reduced to RS485 interfaces standard operating voltage the first Transient Suppression Diode and the second Transient Suppression Diode.The utility model has simple in construction, and reliability is high, excessively stream fast response time, and limit grade is high, and the advantages of automatic recovery ability is strong maintains the proper communication of light current communication system.
Description
Technical field
The utility model is related to the light current communications field, and in particular to a kind of lightning protection for electronic equipment RS485 interfaces is protected
Protection circuit.
Background technology
Many electronic equipments are communicated by RS485 buses, and RS485 buses can realize 1KM long range in theory
Transmission, in application process, long range transmission line is easily because the reason such as thunderbolt, interference introduces high voltage, so as to cause electricity
Sub- device damage.
In light current communication system, the normal working voltage of RS485 transceivers is relatively low (± 2~6V or so), when itself is long
Between pressure-resistant also very low (- 7V~+12V), once high voltage induction, will punch through damage.Occur there is strong surge energy
When, it might even be possible to cause RS485 transceivers to burst, circuit board burns.
General lightning protection device is using one-level or two grades of lightning protections designs, but the voltage of these lightning protections design, electric current
Limit grade and excessively stream response speed are all uneven, and also not comprehensive to the safeguard measure of differential mode, common-mode voltage, cause to prevent
Thunder protecting effect is had a greatly reduced quality.
In summary, existing lightning protection design has the following disadvantages：
(1) voltage, electric current limit grade it is uneven；
(2) excessively stream response speed is uneven；
(3) differential mode, common-mode voltage safeguard measure it is not comprehensive.
Utility model content
Technical problem to be solved in the utility model is voltage, the limit grade of electric current of existing lightning protection design
With excessively stream response speed is uneven and differential mode, the incomplete problem of the safeguard measure of common-mode voltage.
In order to solve the above-mentioned technical problem, the utility model provides a kind of lightning protection for electronic equipment RS485 interfaces
Protection circuit, including first order lightning protection circuit and second level lightning protection circuit, the first order lightning protection circuit include in parallel first
Ceramic gas discharge tube and the second ceramic gas discharge tube, the common-mode voltage of receiving terminal positive pole and the negative pole generation of RS485 interfaces
Discharged over the ground by first ceramic gas discharge tube, the differential mode voltage that receiving terminal positive pole and negative pole are produced passes through described second
Ceramic gas discharge tube discharges；The high current that the second level lightning protection circuit includes suppressing the first order lightning protection circuit output is led to
The current-limiting resistance crossed and the standard operating voltage that the output residual voltage of the first order lightning protection circuit is reduced to RS485 interfaces
First Transient Suppression Diode and the second Transient Suppression Diode.
In the above-mentioned technical solutions, first ceramic gas discharge tube is three pole gas-discharge tubes, and it drains and source electrode
It is connected respectively with receiving terminal positive pole and receiving terminal negative pole, its grounded-grid；Second ceramic gas discharge tube is the two poles of the earth gas
Discharge tube, its one end is connected with receiving terminal positive pole, and the other end is connected with receiving terminal negative pole.
In the above-mentioned technical solutions, the current-limiting resistance includes being serially connected in receiving terminal positive pole and receiving terminal negative pole circuit respectively
On the first thermistor and the second thermistor, first thermistor and the second thermistor are in the first order lightning protection
When the output current of circuit reaches maximum operating currenbt and continues rise, resistance increases rapidly, blocks passing through for big operating current.
In the above-mentioned technical solutions, the maximum operating currenbt of first thermistor and the second thermistor is 250mA,
Pressure-resistant is 600V, and the actuation time of overcurrent protection is 1 second.
In the above-mentioned technical solutions, first Transient Suppression Diode and the second Transient Suppression Diode are bipolarity.
In the above-mentioned technical solutions, one end of first Transient Suppression Diode is connected with receiving terminal positive pole, the other end
It is grounded with one end of second Transient Suppression Diode, the other end and the receiving terminal negative pole of second Transient Suppression Diode
Connection.
In the above-mentioned technical solutions, the grounding resistance of the first order lightning protection circuit and second level lightning protection circuit is no more than 10
Ohm.
The utility model is discharged common-mode voltage and differential mode voltage by first order lightning protection circuit, anti-by the second level
The output residual voltage of first order lightning protection circuit is reduced to the standard operating voltage of RS485 interfaces by thunder and lightning road, with simple in construction, can
High, the excessively stream fast response time by property, voltage, the limit grade height of electric current, continues excessively stream rejection ability is strong, and automatic recovery ability is strong etc.
Advantage, maintains the proper communication of light current communication system.
Brief description of the drawings
Fig. 1 shows for a kind of lightning protection circuit for electronic equipment RS485 interfaces that the utility model embodiment is provided
It is intended to.
Embodiment
The utility model is described in detail with reference to Figure of description.
The utility model provides a kind of lightning protection circuit for electronic equipment RS485 interfaces, as shown in figure 1, bag
First order lightning protection circuit and second level lightning protection circuit are included, first order lightning protection circuit includes the first ceramic gas discharge tube (3R090)
With the second ceramic gas discharge tube (2R090), the first ceramic gas discharge tube meets RS485 as common-mode voltage straining element
The common-mode voltage that the receiving terminal positive pole A and negative pole B of mouth are produced discharges over the ground；Second ceramic gas discharge tube presses down as differential mode voltage
Element processed, discharges the receiving terminal positive pole A and negative pole B differential mode voltages produced；Second level lightning protection circuit include current-limiting resistance,
First Transient Suppression Diode and the second Transient Suppression Diode, current-limiting resistance suppress the high current of first order lightning protection circuit output
By second level lightning protection circuit, when the output current of first order lightning protection circuit reaches the maximum operating currenbt of current-limiting resistance, melt
Disconnected fuse, second level lightning protection circuit protects interface current below into open-circuit condition.First Transient Suppression Diode and second
Transient Suppression Diode is bipolarity, and the standard that the output residual voltage of first order lightning protection circuit is reduced into RS485 interfaces works electric
Pressure.
First ceramic gas discharge tube be three pole gas-discharge tubes, its drain and source electrode respectively with receiving terminal positive pole and reception
Hold negative pole connection, its grounded-grid；Second ceramic gas discharge tube is the two poles of the earth gas-discharge tube, with the first ceramic gas discharge tube
One end is connected with receiving terminal positive pole A after parallel connection, and the other end is connected with receiving terminal negative pole B.
Current-limiting resistance include being serially connected in respectively the first thermistor on receiving terminal positive pole A and receiving terminal negative pole B circuits and
The maximum operating currenbt of second thermistor, the first thermistor and the second thermistor is 250mA, and pressure-resistant is 600V, excessively stream
The actuation time of protection is 1 second, when the output current of first order lightning protection circuit reaches maximum operating currenbt and continues rise, the
The resistance of one thermistor and the second thermistor increases rapidly, so as to block passing through for big operating current, plays the big work of limitation
Make the effect of electric current.
One end of first Transient Suppression Diode is connected with receiving terminal positive pole A, the other end and the second Transient Suppression Diode
One end ground connection, the other end of the second Transient Suppression Diode is connected with receiving terminal negative pole B.
The operation principle of first order lightning protection circuit is：
When the RS485 interface normal works of electronic equipment, the first ceramic gas discharge tube and the second ceramic gas discharge
Pipe does not work.When the RS485 interfaces of electronic equipment are struck by lightning, the common-mode voltage of the receiving terminal positive pole A sensings of RS485 interfaces
VAThe common-mode voltage V sensed with receiving terminal negative pole BBDischarged over the ground by the first ceramic gas discharge tube, common-mode voltage VAAnd common mode
Voltage VBAbout 90V or so is impaired to after discharging over the ground；The differential mode voltage of receiving terminal positive pole A and negative pole the B sensing of RS485 interfaces
VABDischarged by the second ceramic gas discharge tube, differential mode voltage VABAbout 90V or so is impaired to after electric discharge.First order thunder-lightning
The primary protection on road forms the voltage protection of the 90V grades when dc breakdown voltage is 100V/S, and the grade of voltage is limited
90V or so is arrived.
First ceramic gas discharge tube can use EPCOS T83-A90, and the second ceramic gas discharge tube can use EPCOS
N81-A90, dc breakdown voltage is 90V ± 20%, impact flashover voltage<450V (1kV/ μ s), impact resistance electric current (2/10 μ s)
10kA, response time<0.2μs.First ceramic gas discharge tube and the second ceramic gas discharge tube are in typically electric discharge (10/1000 μ
S 200A) when, there can be the electric discharge service life of 100~200 times.
The first ceramic gas discharge tube and the second ceramic gas discharge tube in this programme can bear great Lei energy and hit, but
Be but can not in the primary protection of first order lightning protection circuit will thunderbolt voltage clamp can be born to general RS485 transceivers
Voltage level, accordingly, it would be desirable to carry out second level protection.
The operation principle of second level lightning protection circuit is：
Connected respectively in the receiving terminal positive pole A and negative pole B of RS485 interfaces and access the first thermistor (TSM600-250F-
RA) and the second thermistor (TSM600-250F-RA), the maximum operating currenbt of the first thermistor and the second thermistor is
250mA, realizes voltage clamp to after 90V in first order lightning protection circuit, receiving end is being achieved a butt joint just by second level lightning protection circuit
Pole A and the overcurrent protection on negative pole B two lines road.
When the RS485 interface normal works of electronic equipment, the electric current of the first thermistor and the second thermistor is flowed through
Very little, is not enough to cause the temperature rise of the first thermistor and the second thermistor, when big caused by common-mode voltage and differential mode voltage
When electric current is by the first thermistor and the second thermistor, the first thermistor and the second temperature increment on thermal resistor become big, cause
The cataclysm of resistance, suppresses the purpose that high current passes through so as to play, also protects follow-up element.
First Transient Suppression Diode (1.5KW 6.8V) and the second Transient Suppression Diode (1.5KW6.8V) are by the first order
The output residual voltage of lightning protection circuit is clamped down in 6.8V or so, close to the standard operating voltage of RS485 interfaces, realizes and RS485 is connect
The protection of mouth.Meanwhile, can be real by changing the type selecting parameter of the first Transient Suppression Diode and the second Transient Suppression Diode
Weak electric signal protection of the existing voltage class from 5V to 24V.
First thermistor and the second thermistor can use TYCO SM600-250F-RA as resettable fuse,
TYCO SM600-250F-RA maximum operating currenbt is 250mA, and pressure-resistant is 600V, and the actuation time of overcurrent protection is 1 second.When
When surge disappears, the temperature of the first thermistor and the second thermistor is gradually reduced, and finally returns to 3 ohm of normal resistance
Value, 485 communication lines also slowly recover normal in this process.Due to the first thermistor and the normal work of the second thermistor
Resistance is 3 ohm when making, and the communication quality of 485 communication lines is had little to no effect, so being particularly suitable for long range, multinode
Access environment.
First order lightning protection circuit and second level lightning protection circuit are grounded, and grounding resistance is no more than 10 ohm, so as to
Greatly improve lightning protection effect.
The protection class for the lightning protection circuit that this programme is provided is as follows：
Thunder-strike prevention standard：YD/T993-2006 4.0KV；Surge capacity：1500W；Surge current：200A；Excessively stream short-circuit protection
Ih：250mA.
The utility model is discharged common-mode voltage and differential mode voltage by first order lightning protection circuit, anti-by the second level
The output residual voltage of first order lightning protection circuit is reduced to the standard operating voltage of RS485 interfaces by thunder and lightning road, with simple in construction, can
High by property, service life is long, excessively stream fast response time, voltage, the limit grade height of electric current, continues excessively stream rejection ability by force, from
The advantages of recovery capability is strong, maintains the proper communication of light current communication system.
The utility model is not limited to above-mentioned preferred forms, and anyone should learn that under enlightenment of the present utility model
The structure change made, it is every that there is same or like technical scheme with the utility model, each fall within guarantor of the present utility model
Within the scope of shield.
Claims (7)
1. a kind of lightning protection circuit for electronic equipment RS485 interfaces, it is characterised in that including first order lightning protection circuit and
Second level lightning protection circuit, the first ceramic gas discharge tube and the second ceramic gas that the first order lightning protection circuit includes parallel connection is put
Fulgurite, the common-mode voltage that the receiving terminal positive pole and negative pole of RS485 interfaces are produced by first ceramic gas discharge tube over the ground
The differential mode voltage that electric discharge, receiving terminal positive pole and negative pole are produced is discharged by second ceramic gas discharge tube；The second level
Current-limiting resistance that the high current that lightning protection circuit includes suppressing first order lightning protection circuit output passes through and by the first order
The output residual voltage of lightning protection circuit is reduced to the first Transient Suppression Diode and the second transient state of the standard operating voltage of RS485 interfaces
Suppress diode.
2. circuit as claimed in claim 1, it is characterised in that first ceramic gas discharge tube is three pole gas discharges
Pipe, it drains and source electrode is connected with receiving terminal positive pole and receiving terminal negative pole respectively, its grounded-grid；Second ceramic gas is put
Fulgurite is the two poles of the earth gas-discharge tube, and its one end is connected with receiving terminal positive pole, and the other end is connected with receiving terminal negative pole.
3. circuit as claimed in claim 1, it is characterised in that the current-limiting resistance include being serially connected in respectively receiving terminal positive pole and
The first thermistor and the second thermistor on receiving terminal negative pole circuit, first thermistor and the second thermistor exist
When the output current of the first order lightning protection circuit reaches maximum operating currenbt and continues rise, resistance increases rapidly, blocks big
Operating current passes through.
4. circuit as claimed in claim 3, it is characterised in that the maximum work of first thermistor and the second thermistor
Make electric current for 250mA, pressure-resistant is 600V, and the actuation time of overcurrent protection is 1 second.
5. circuit as claimed in claim 1, it is characterised in that first Transient Suppression Diode and the second transient state suppress two
Pole pipe is bipolarity.
6. circuit as claimed in claim 1, it is characterised in that rectify with receiving one end of first Transient Suppression Diode
Pole is connected, and one end of the other end and second Transient Suppression Diode is grounded, second Transient Suppression Diode it is another
End is connected with receiving terminal negative pole.
7. circuit as claimed in claim 6, it is characterised in that the first order lightning protection circuit connects with second level lightning protection circuit
Ground resistance is no more than 10 ohm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201720248410.7U CN206533129U (en) | 2017-03-14 | 2017-03-14 | A kind of lightning protection circuit for electronic equipment RS485 interfaces |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201720248410.7U CN206533129U (en) | 2017-03-14 | 2017-03-14 | A kind of lightning protection circuit for electronic equipment RS485 interfaces |
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| Publication Number | Publication Date |
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| CN206533129U true CN206533129U (en) | 2017-09-29 |
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ID=59914685
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| Application Number | Title | Priority Date | Filing Date |
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| CN201720248410.7U Active CN206533129U (en) | 2017-03-14 | 2017-03-14 | A kind of lightning protection circuit for electronic equipment RS485 interfaces |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107634510A (en) * | 2017-09-30 | 2018-01-26 | 深圳市艾特智能科技有限公司 | Chip interface circuit |
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2017
- 2017-03-14 CN CN201720248410.7U patent/CN206533129U/en active Active
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107634510A (en) * | 2017-09-30 | 2018-01-26 | 深圳市艾特智能科技有限公司 | Chip interface circuit |
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