1.TVS diode characteristic:

 

Diode of TVS(Transient Voltage Suppressor) , say transient state restrains diode again, it is parts of an apparatus of protection of a kind of when use generally new-style and efficient circuit, when it has splitting noise to answer (inferior accept second class) absorb ability with quite tall surge.

 

When the high energy that endures the moment when its two end is pounded, TVS can turn into the impedance value between two end by tall impedance with extremely high rate low impedance, in order to absorb an instant big electric current, on the numerical value that books strangulation of its two upright voltage in, protect the circuit element from the back not to suffer the concussion of pulse of aiguille of transient state high pressure thereby. The electrostatic concussion that conducts loop in rate of processing high speed from time to tome better property performance.

 

 

2.The application of TVS diode:

 

1, the application in alternating current road

The graph is shown 1 times is a two-way TVS the applied circuit in alternating current road. Applied TVS restrains the overload pulse that electrified wire netting brings effectively, in rising to protect rectification bridge and load thereby all yuan of action of parts of an apparatus. Graph 1 medium TVS Qian what voltage should not be more than circuit is the biggest allow voltage.

 

Graph 1 two-way TVS is communicating the applied circuit in circuit

 

2, protect dc regulated power supply with TVS

Graph 2 it is regulated power supply of a dc, in its stabilized voltage outputs end to add TVS, can protect the instrument device that uses this power source, the collector that still can absorb the transistor in circuit at the same time arrives blast off extremely the peak value voltage between, protect transistor thereby. Suggest the output end in source of every stabilized voltage increases canal of a TVS, can raise overall dependability substantially so.

 

Graph 2 TVS protects dc regulated power supply

3, protect transistor circuit with TVS

 

All sorts of twinkling change voltage can make the EB knot of transistor or CE knot puncture and attaint, especially transistor collector has sensibility (coil, transformer, electromotor) when load, normally meeting generation high pressure opposes electromotive force, consequently the likelihood makes transistor damages. In applying actually, the proposal uses TVS to regard protection as parts of an apparatus. The graph shows the example of 4 kinds of circuit that protects transistor for TVS 3 times.

 

Graph 3 TVS protects transistor circuit

 

4, with TVS protection compositive carry is put

 

Compositive carry is put very sensitive to outside report stress. Accordingly, in the process that puts in use carry, if because operate error or accepted abnormal working condition, often can have appeared big voltage or electric current, especially surge and electrostatic pulse, make carry puts damage or invalidation very easily thereby. The graph is shown 4 times is the protective circuit that puts wrong standard to input end to had prevented to control damage in carry with TVS.

 

The protective circuit that graph 4 TVS is carrying the model that put difference inputs end to had prevented to control damage

 

 

3.TVS canal and element of other circuit protection are comparative

 

1, TVS diode and stabilized voltage diode:

 

TVS diode and stabilized voltage diode are in circuit is to be received reversely, use its retrorse character namely, use effect of PN knot avalanche, there all is a critical voltage before retrorse puncture, receiving circuit to have stabilized voltage effect reversely, but endless also and identical, what stabilized voltage diode uses is secure input voltage in a certain numerical value, and TVS diode basically is to prevent circuit of the class after transient state high pressure is right to undertake clamp;

 

Stabilized voltage diode won’t be told commonly answer time, more it is value of attention stabilized voltage, but different to TVS diode, its character is deciding it to have distinct effect, TVS diode has transient state to control high energy function, because this asks to absorb higher energy instant inside shorter time, this time is very accordingly short, reach accept second level;

 

The power of stabilized voltage diode is not very big commonly, common stabilized voltage diode has 1W, 2W to wait, the temperature rise that its power allows by it decides, actual the product that is stable voltage and electric current, for example to 1N4742A of stabilized voltage diode, its power has 1W only greatly most, stabilized voltage value is 12V, cannot exceed 80mA commonly through its electric current so, or what pipe can give out heat is fierce; To TVS diode, its cultured is instantaneous pulse power, this power cost is very high, can achieve on kilowatt, it is this time value is maintained only very small.

 

Pursue on: MMSZ5231B-7-F of stabilized voltage diode

Vz=5.1V, 0.5W, ±5%

 

2, TVS diode and pressure quick resistor, gas discharge tube:

 

On reaction time, pressure quick resistor interpose is in charge of at TVS and between gas discharge tube, TVS runs course of the second that it is a skin, pressure quick resistor slightly slow, for accept second class; And gas discharge tube is the slowest, it is second of a few accept normally more even.

 

Connecting shed a capacity, press quick report to upright to be mixed at TVS likewise between gas discharge tube, TVS canal has hundreds of A; only normally and press quick resistor presses different specifications, can arrive through counting KA the sheet of tens of KA second 8/20uS surge electric current; And normally to gas discharge tube electric current of surge of 8/20uS of 10 KA level can guide connect hundreds times.

 

Look from the principle, TVS canal is based on diode avalanche effect; Pressure quick resistor is based on the power base action between zinc oxide grain; And gas discharge tube is to be based on aeriform puncture discharge.

 

In voltage limits respect, TVS canal is pressed to 550V; for 5.5V normally quick the range of resistor is wider, but from 10V to 9000V; gas discharge tube can arrive from 75V 3500V.

 

What TVS is in charge of is nonlinear character and stabilized voltage valve are same, the leakage current before puncture is very small, the stabilized voltage that the standard is after puncture is characteristic, compared with pressure quick resistance comes TVS is in charge of the biggest Qian voltage of voltage deviate puncture is lesser, excel is pressed quick resistor, but shed ability comparing to press quick resistor is lesser.

 

Pressure quick resistor can bear bigger surge electric current, and its volume is larger can susceptive surge electric current is bigger, can amount to a few KA to arrive most about a hundred KA; Of Dan Yamin resistor nonlinear character is wronger, voltage of the limitation when big electric current is taller, electric current of low voltage hourglass is bigger.

 

Pursue on: Pressure quick resistor V0603MHS12NH

55V 0603

 

3, TVS diode and capacitance of pottery and porcelain:

 

Personnel of a lot of designs is willing to use the surface to stick the capacitance of pottery and porcelain of outfit to make ESD protect, not only cheap and the design is handy, but this kind of parts of an apparatus is right of high pressure bear force is weaker however. The concussion of 5kV can create be no longer in force of capacitance of about 10% pottery and porcelain, arrive when 10kV, attaint rate is achieved 60% , and TVS diode can bear 15kV voltage. In the use process that holds facility, because be contacted often with human body, each port must can bear at least 8kV contacts concussion (IEC61000-4-2 standard) , diode of visible use TVS can assure the percent of pass of end item effectively.

 

Pursue on: Capacitance of pottery and porcelain CL21B104KACNNNC

 

4, TVS diode and MLV:

 

Multilayer parts of an apparatus of metallic oxide structure (MLV) also can undertake impact of significant instantaneous high pressure is restrained, this kind of parts of an apparatus is had nonlinear voltage – electric current (impedance is behaved) relation, the 2 ～ that cut-off voltage can amount to first pause voltage 3 times, this kind of character suits to be used at the protection of not quite sensitive to voltage circuitry and parts of an apparatus, be like power source loop. And TVS transient state restrains diode to have better voltage to end factor, still have inferior electric capacity at the same time, this are very important to holding the high frequency port of equipment, because exorbitant capacitance can affect data to transmit, cause lack fidelity or it is to demote.

 

5, epilogue

 

TVS transient state restrains all sorts of surfaces of diode to enclose the requirement that all fits automation line to assemble, and chip structure facilitates the function of compositive other, filter like EMI and RFI protection, can reduce cost of parts of an apparatus effectively, optimize integral design.

 

Another cannot the characteristic of oversight is diode can very conveniently as compositive as other parts of an apparatus go up in a chip, a lot of more existing filter EMI defend with RFI etc function and TVS are compositive the parts of an apparatus that be together, not only the number of parts of an apparatus that reduces design place to use reduces cost, and when also avoiding the wiring on PCB board easy the companion that cause is born to feel oneself.