Module 4 thyristors

Thyristors

CharacteristicsHysteresis character

◦It latches to its last position, on or off◦Example, physical s/w – you s/w it

on, it remains on.May be viewed as 2 transistors

working in pair.Constructed from bipolar junction

technology.

Examples of ThyristorsShockley diodeDIACSCR (silicon controlled rectifier)TRIACOpto thyristors

Shockley DiodeNot to be confused with schottky

diodeIt is a four layer device

Also known as PNPN diode.

The Working of the Shockley DiodeThe four PNPN can be simplified

to two set of separate transistors, PNP and NPN.

P P

N

N

NP

With high voltage, one of the transistor will be turned on causing the other to be on. Once on, the transistors latched. To turn off, the voltage must be reduced to cause the current to drop below minimum

DIACShockley diode works with DC.For AC, 2 shockleys are joint.The result is shown in the lower

image

SCRSilicon Controlled Rectifiers or

thyristors.Used to rectify AC and control the

power output.

TRIAC Dimmer

TRIAC FOR AC

Opto- tyristors

RESOURCES

Title Author

Aircraft Electricity and Electronics

Eisman 0-02-801859-1

Art of Electronics Horowitz /Hill

Horowitz /Hill

0-521-37095-7

Elements of Electronics

Hickey/ Villines

0070286957

Modern Aviation Electronics

Helfrich 0-13-118803-8

Micro Electronics in Aircraft systems

E Pallet 0-273-08612-X

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