Thyristors

ET5

RecapThere have been a few different circuit switching methods we have covered during ET1, ET2, ET4 and ET5 with each having its own specific purpose.

Think back to ET3 when you were creating a Software Switch as a Latch. The system was latched on by a software switch linked to the output at the end of ladder. Once the original digital input was switched off, the system still stayed on caught in a feedback loop. This is the effect of latching.

The behaviour of a ThyristorThyristors are basically diodes that require a maintenance current to keep them operational. They are used in a forward biased direction (unlike Zener diodes) and begin to let current flow only when they receive a current from another sub system.

Alternating Current

DIac

Thyristor

HysteresisThyristors are a class of semiconductor components exhibiting hysteresis, that property whereby a system fails to return to its original state after some cause of state change has been removed. A very simple example of hysteresis is the mechanical action of a toggle switch: when the lever is pushed, it flips to one of two extreme states (positions) and will remain there even after the source of motion is removed (after you remove your hand from the switch lever).

Quote: www.allaboutcircuits.com