CN205754271U - The protection circuit of RS485 based on Phototube Coupling - Google Patents
The protection circuit of RS485 based on Phototube Coupling Download PDFInfo
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- CN205754271U CN205754271U CN201620577926.1U CN201620577926U CN205754271U CN 205754271 U CN205754271 U CN 205754271U CN 201620577926 U CN201620577926 U CN 201620577926U CN 205754271 U CN205754271 U CN 205754271U
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- mode choke
- isolation optocoupler
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Abstract
The utility model discloses the protection circuit of a kind of RS485 based on Phototube Coupling, protect loop including RS485 chip, common mode choke and EDS；Two input ports of common mode choke connect the driver output end mouth of RS485 chip；Two output ports of common mode choke connect A bus transfer port and B output end of main mouth；EDS protection loop is connected between the output port of common mode choke and two bus transfer ports；Described RS485 chip is isolated form chip；Or RS485 chip is the isolation optocoupler also including in non-isolation type chip and protection circuit being connected between CUP communication chip and RS485 chip.This utility model takes high speed photo coupling isolation, TVS pipe protection in common RS485 circuit, and matches the measures such as 120 Ω build-out resistors and common mode choke.Test proves that, circuit performance is obviously improved that there is good practicality.
Description
Technical field
This utility model relates to communication interface protection circuit, is specifically related to the protection of a kind of RS485 based on Phototube Coupling
Circuit.
Background technology
RS-485 allows to carry out multiple spot, two-way communication on simple a pair twisted-pair feeder, the noise suppressed energy that it is had
Power, message transmission rate, cable length and reliability are that other standards is incomparable.The most so, as a kind of multiple spot, difference
Point the electrical code of data transmission become one of standard communication interface that industry is most widely used.
Fig. 1 is RS485 circuit diagram of the prior art.
In FIG, owing to due to the characteristic of RS-485 chip, the detection sensitivity of receptor is ± 200mV, and two are driven
When dynamic device output port A end, the absolute value of B terminal potential difference are less than 200mV, it is output as uncertain.In order to solve this problem, in
It is artificial to pull up current potential, the drop-down current potential of B end at A end, so can present unique level by line during bus does not sends, it is to avoid receive
To random character.And in FIG, side a and b is all serially connected with the resistance of 20 Ω, makes side a and b and Bus isolation, to avoid when one
When 485 chips of platform extension set are breakdown, in bus, other extension set is affected, in signal output part series connection as shown in Figure 1
After the resistance of two 20 Ω, this sample fault would not make the communication of whole bus be affected.
Utility model content
On the basis of existing technology, the utility model discloses the protection circuit of a kind of RS485 based on Phototube Coupling.
The technical solution of the utility model is as follows:
The protection circuit of a kind of RS485 based on Phototube Coupling, protects including RS485 chip, common mode choke and EDS
Loop；RS485 chip includes driver output end mouth, driver input end mouth, receptor output port and enable port；
Two input ports of common mode choke connect the driver output end mouth of RS485 chip；The two of common mode choke
Individual output port connects A bus transfer port and B output end of main mouth；
EDS protection loop is connected between the output port of common mode choke and two bus transfer ports, and EDS protects back
Road includes three Zener diodes, and the positive pole of three Zener diodes is both connected to together, the first Zener diode and second steady
The negative pole of pressure diode is connected to the first output port of common mode choke, and the negative pole of the 3rd Zener diode is connected to common mode and grips
Second output port of stream device；
Described RS485 chip is isolated form chip；Or RS485 chip is also to wrap in non-isolation type chip and protection circuit
Include the isolation optocoupler being connected between CUP communication chip and RS485 chip.
Its further technical scheme is, when RS485 chip is isolated form chip, the model of RS485 chip is
ADM2483 or ADM2587E.
Its further technical scheme is, when protection circuit includes isolating optocoupler, isolation optocoupler includes the first isolation
Optocoupler, the second isolation optocoupler and the 3rd isolation optocoupler；First be optically isolated coupling be connected on CPU communication pin input port and
Between the receptor output port of RS485 chip；Second be optically isolated coupling be connected on CPU communication pin output port and
Between the enable port of RS485 chip；3rd is optically isolated output port and the RS485 chip coupling the communication pin being connected on CPU
Driver input end mouth between；First isolation optocoupler and the 3rd isolation optocoupler are high speed photo coupling.
Its further technical scheme is, the model of the first isolation optocoupler and the 3rd isolation optocoupler is PC410L0NIP, the
The model of two isolation optocouplers is PC/817.
Its further technical scheme is, when RS485 chip is non-isolation type chip, the model of RS485 chip is
75176BDR。
Its further technical scheme is, connecting between A bus transfer port and B output end of main mouth has 120 ohm
Resistance.
Advantageous Effects of the present utility model is:
This utility model takes high speed photo coupling isolation, TVS pipe protection in common RS485 circuit, and matches 120 Ω
The measure such as build-out resistor and common mode choke.Test proves that, circuit performance is obviously improved have good
Practicality.Circuit injection test pulse resistance test (Electrical fast transients) is tested, existing skill in Fig. 1
The circuit voltage of art can be with injection to ± 2KV, and the circuit of the present utility model shown in Fig. 2, and injection voltage can reach ±
4KV。
Accompanying drawing explanation
Fig. 1 is RS485 circuit diagram of the prior art.
Fig. 2 is circuit diagram of the present utility model.
Detailed description of the invention
Fig. 2 is circuit diagram of the present utility model.As in figure 2 it is shown, this utility model includes RS485 chip IC 20, is total to
Mould choke L9 and EDS protects loop.RS485 chip IC 20 includes two driver output end mouth A, B, driver input end
Mouth D, receptor output port R and enable port DE, RE.
In the present embodiment, the model of common mode choke L9 is OCF3216900, is that common code impedance is 90ohm when 100M
Common mode choke.485 order wires are made up of the line of two multiple twins, transmit signal by the voltage difference between two order wires,
Therefore differential voltage transmission it is referred to as.Common mode disturbances is to transmit between holding wire and ground, belongs to asymmetry interference.In output
Use common mode choke on line, can first reduce the common mode disturbances of signal.
Two input ports of common mode choke L9 connect two driver output end mouth A of RS485 chip IC 20 respectively,
B.Two output ports of common mode choke L9 connect A bus transfer port and B output end of main mouth.
EDS protection loop is connected between the output port of common mode choke L9 and two bus transfer ports.Concrete,
EDS protection loop includes three Zener diodes, and the positive pole of three Zener diodes is both connected to together, the first Zener diode
The negative pole of ZD2 is connected to the first output port of common mode choke L9, and the negative pole of the second Zener diode ZD3 passes through electric capacity C134
Being connected to the first output port of common mode choke L9, the negative pole of the 3rd Zener diode ZD4 is connected to common mode choke L9
Second output port.The on-the-spot interference source often having many forms, three Zener diodes ZD2, ZD3, ZD4 are that TVS transient state is miscellaneous
Ripple suppression device, forms ESD protection loop, is that the transmission ends of 485 buses adds protective measure.
RS485 chip IC 20 can be isolated form chip, if selecting isolated form RS485 chip, can be selected for model is
The RS485 chip of ADM2483 or ADM2587E, isolated form 485 chip ADM2483 be internally integrated a three-channel magnetic every
From device and half-duplex 485 transceiver, it has 2500V isolation voltage, and transfer rate is 500K, common-mode voltage suppression energy
Power is 25KV/ μ S.But this circuit still needs to dual power supply.Also single supply isolated form 485 chip of completely isolated type can be used
ADM2587E。
RS485 chip IC 20 can also select non-isolation type chip, as can be selected for the core of the RS485 that model is 75176BDR
Sheet.Now, protection circuit also should increase the isolation optocoupler being connected between CUP communication chip and RS485 chip.
Isolation optocoupler includes the first isolation optocoupler PC11, the second isolation optocoupler PC12 and the 3rd isolation optocoupler PC13.First
It is optically isolated between input port and the receptor output port R of RS485 chip of the communication pin that coupling is connected on CPU；Second every
It is connected to from optocoupler between output port and enable port DE, RE of RS485 chip of the communication pin of CPU；3rd is optically isolated
Between output port and the driver input end mouth D of RS485 chip of the communication pin that coupling is connected on CPU.In actual application
In, in order to provide the baud rate of communication, the first isolation optocoupler PC11 and the 3rd isolation optocoupler PC13 is high speed photo coupling.
In the present embodiment, the model of the first isolation optocoupler PC11 and the 3rd isolation optocoupler PC13 is PC410L0NIP, the
The model of two isolation optocoupler PC12 is PC/817.
As preferred technical scheme, in this utility model, connect between A bus transfer port and B output end of main mouth
It is connected to the resistance R206 of 120 ohm.
In the scene of application system, communications carrier is twisted-pair feeder, and its characteristic impedance is about 120 Ω, so line
During the design of road, respectively should connect the build-out resistor of 1 120 Ω at the top of Network transmission line and end, to reduce transmission letter on circuit
Number reflection.Due to build-out resistor larger current to be consumed, thus general only in communication distance use more than 100 meters, thus electric
Resistance selects resistance for sheet.
Above-described is only preferred implementation of the present utility model, and this utility model is not limited to above example.Can
To understand, those skilled in the art directly derive or associate on the premise of without departing from spirit of the present utility model and design
Oher improvements and changes, within being all considered as being included in protection domain of the present utility model.
Claims (6)
1. the protection circuit of a RS485 based on Phototube Coupling, it is characterised in that include RS485 chip, common mode choke with
And EDS protects loop；RS485 chip includes driver output end mouth, driver input end mouth, receptor output port and makes
Can port；
Two input ports of common mode choke connect the driver output end mouth of RS485 chip；Two of common mode choke defeated
Go out port and connect A bus transfer port and B output end of main mouth；
EDS protection loop is connected between the output port of common mode choke and two bus transfer ports, EDS protection loop bag
Including three Zener diodes, the positive pole of three Zener diodes is both connected to together, the first Zener diode and the second voltage stabilizing two
The negative pole of pole pipe is connected to the first output port of common mode choke, and the negative pole of the 3rd Zener diode is connected to common mode choke
The second output port；
Described RS485 chip is isolated form chip；Or RS485 chip is also to include even in non-isolation type chip and protection circuit
The isolation optocoupler being connected between CUP communication chip and RS485 chip.
2. the protection circuit of RS485 based on Phototube Coupling as claimed in claim 1, it is characterised in that when RS485 chip is
During isolated form chip, the model of RS485 chip is ADM2483 or ADM2587E.
3. the protection circuit of RS485 based on Phototube Coupling as claimed in claim 1, it is characterised in that when in protection circuit
During including isolation optocoupler, isolation optocoupler includes the first isolation optocoupler, the second isolation optocoupler and the 3rd isolation optocoupler；First is optically isolated
Between input port and the receptor output port of RS485 chip of the communication pin that coupling is connected on CPU；Second is optically isolated coupling
It is connected between output port and the enable port of RS485 chip of the communication pin of CPU；3rd is optically isolated coupling is connected on CPU's
Between output port and the driver input end mouth of RS485 chip of communication pin；First isolation optocoupler and the 3rd isolation optocoupler
For high speed photo coupling.
4. the protection circuit of RS485 based on Phototube Coupling as claimed in claim 3, it is characterised in that the first isolation optocoupler
Being PC410L0NIP with the model of the 3rd isolation optocoupler, the model of the second isolation optocoupler is PC/817.
5. the protection circuit of RS485 based on Phototube Coupling as claimed in claim 1, it is characterised in that RS485 chip is non-
During isolated form chip, the model of RS485 chip is 75176BDR.
6. the protection circuit of the RS485 based on Phototube Coupling as described in any one of Claims 1 to 5, it is characterised in that A is total
Connect, between line transmission port and B output end of main mouth, the resistance having 120 ohm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201620577926.1U CN205754271U (en) | 2016-06-13 | 2016-06-13 | The protection circuit of RS485 based on Phototube Coupling |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201620577926.1U CN205754271U (en) | 2016-06-13 | 2016-06-13 | The protection circuit of RS485 based on Phototube Coupling |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN205754271U true CN205754271U (en) | 2016-11-30 |
Family
ID=57386495
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201620577926.1U Active CN205754271U (en) | 2016-06-13 | 2016-06-13 | The protection circuit of RS485 based on Phototube Coupling |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN205754271U (en) |
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2016
- 2016-06-13 CN CN201620577926.1U patent/CN205754271U/en active Active
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| GR01 | Patent grant |