1. Control characteristics of thyristors and triacs

Thyristors, which are trigger-only controlled components, are the oldest controlled power semiconductor components (late 1950s). They are normally unidirectional in current and bidirectional in voltage, but come in a number of technological variants, notably asymmetrical thyristors, which can withstand very low reverse voltages but are faster to turn off (currently used for pulsed applications and resonant inverters). They are sometimes integrated with an antiparallel diode (reverse-conduction thyristors). There are also so-called bidirectional thyristors (on the same chip, two thyristors are integrated head-to-tail, BCT for Bidirectionally Controlled Thyristors). Since thyristors cannot be controlled, they are blocked when the current is cancelled, requiring a minimum reverse voltage application time of t _q . As a result, thyristors are mainly...