The surge effect to circuit

 

Surge includes voltage of surge electric current, surge, it is to point to to the phenomenon that exceeds regular job voltage, electric current appears for an instant in circuit. In industrial newsletter spot, thunder overvoltage, fall the revulsive thunder surge that Lei Yin gives out, still have power source system (take very heavy perceptual load especially) the surge that switch switch causes, the transient state that these surge produce is pressed too and flow too, can bring about network of communication of data bus line to break down to make even yuan of signal that parts of an apparatus issues a mistake, can bring very big loss to the user.

 

Express a few kinds of 1 comparison that transient state annoys

 

The transient state that knows a few kinds of types first annoys: From inside the watch knowable, the energy of surge is highest, pass electricity the biggest, because this endangers a gender,also be the biggest.

 

The formation of surge has two kinds: One is in all model, one needs a standard. Thunder or the surge that produce when voltaic switch greatly are commonly in all of the model; Because there is course of high tension line near data cable,the surge of wrong standard form often is, between data wire cable and high tension line because be isolated from undesirable and of generation, the meeting is longer in data communication network the stability inside time exists. The compression with smooth Ou or magnetism Ou nominal parts of an apparatus is in all model, namely front arrives the compression between back end. If exceed this compression, front back end burns out together; Yuan parts of an apparatus won’t be nominal the compression of wrong standard, ability of wrong standard compression is decided by the design of circuit, wrong standard voltage exceeds circuit to bear limits, front is burned-out, back end won’t be burned-out.

 

At present bus line surge defends plan has two kinds: Use component yuan parts of an apparatus is built or use compositive module.

 

 Groovy surge defends plan —— distributes cubic record

 

A lot of application ask to satisfy IEC61000-4-2 electrostatic discharge 4 class, IEC61000-4-5 surge fights faze 4 class requirement. Send and receive commonly implement of ESD, surge defend grade all is compared low, if CTM1051M keeps apart CAN to close implement segregation compression is 2500VDC, below bare chance circumstance, grade of ESD, surge all inferior, be necessary to add periphery circuitry so.

 

Prevent surge circuit to divide normally for: Keep apart law and avoid law.

 

● keeps apart a law: Use opto-coupler or magnetism coupler, keep apart input and output signal departure, law of this kind of segregation can be restrained only in all the surge of modular form, cannot restrain the surge of wrong standard form.

● avoid law: Advocate the ground of equipment forms sheet to nod ground connection together repeatedly, once surge appears but energy of safe move surge, in addition be necessary to increase a few parts of an apparatus that control surge, basically have Tvs canal, pressure quick resistor, gas discharge tube.

 

If will keep apart law and union of avoid law photograph, OK better protection system. Avoid parts of an apparatus can restrain surge to protect segregation parts of an apparatus on one hand, also can restrain the surge of wrong standard form of the generation on bus line. Segregation parts of an apparatus is restrained in all modular form surge, protect advocate equipment. Both supplement each other, can protect bus line facility better. It is with CAN bus line exemple, next graphs are schism yuan the periphery that parts of an apparatus forms protects circuit.

 

Bus line of graph 1 CAN recommends protective circuit

 

Among them GDT park is foremost upright, offer one class to defend, when be struck by lightning, surge arises, GDT instant achieves low block status, for instantaneous big electric current offers release channel, it is clamp down on of the voltage between CAN_H, CAN_L inside limits of two bend over. Take a value actually to be able to undertake adjustment according to defending grade and cost of parts of an apparatus consider integratedly, r3 and R4 proposal choose PTC, d1~D6 suggests to choose fast restore diode. Parameter is expressed as follows.

 

Express 2 parameter to recommend a watch

 

Efficient surge defends plan of plan —— module

 

Schism yuan although plan of parts of an apparatus can be offerred defend effectively, but need introduces more electronic parts, this also means interface circuit to will take up more PCB spaces, create EMC problem if choice of parameter of parts of an apparatus is improper easily. more concise defend design? The answer is affirmative. The signal surge that can choose to introduce major is restrained implement SP00S12, can use at all sorts of signal to transmit a system, restrain be struck by lightning, surge, press too wait for harmful signal, undertake protective to equipment signal port. The keeps apart CTM or SC series completely segregation CAN of tie-in ZLG is sent and receive implement, pursue as follows. But of the promotion product of great rate compositive degree, hereat at the same time the contractible development cycle of great rate.

 

Graph 2 module plan

 

Plan contrast and surge immunity to interference check

 

Bus line surge is told to defend plan has two kinds in front, sum up next:

 

● schism yuan plan of parts of an apparatus: Electronic parts is much, build troublesome, complex, take up create EMC problem PCB space, easily;

● module plan: Use space of convenient, economic PCB, simplify circuit.

 

Do test of surge immunity to interference next, examine surge is restrained implement whether contented IEC61000-4-5±4KV defends requirement, with in all modular surge test is exemple, in SP00S12 the input carries voltage of surge of to load 4KV, 1.2/50μs, in output end test pressing falls to already was reduced to come 17.1V, undee plan is as follows.

 

Graph 3 inputs carry voltage weaveform 4KV

 

Graph 4 output carry undee voltage 17.1V

 

This shows, in send and receive implement as total as CAN space adds SP00S12, the surge grade that can make CAN signal port satisfies IEC61000-4-5 ±4KV easily asks.

 

The tall surge that uses unifinication defends segregation CAN is sent and receive implement can replace segregation CAN completely to send and receive implement restrain with surge implement combination, pursue as follows. This plan simplifies utmost space of circuit design, economic PCB, reduce product cost. It can defend admirable EMC character still is had while 4KV surge, 15KV is electrostatic.

 

Graph 5 unifinication keep apart plan