This document describes a trigger circuit for triggering the TRIAC in the second and third quadrants in a system using a positive power supply. New series TRIACs can replace conventional TRIACs by simply adding a capacitor and a diode.
This document details a method to trigger TRIACs in the second and third quadrants (QII and QIII) using a positive power supply. The proposed circuit utilizes a discharge capacitor and a diode to generate a negative gate current pulse required for triggering these specific quadrants.
The circuit requires a minimum gate current pulse width of 20 us to ensure proper triggering.
The maximum latching current is 50 mA for these specific TRIACs and quadrants.
The capacitor acts as an open circuit for dc current, which avoids all triggering.