amplified triac drive

elektorjuly/august 1983 57 amplified triac drive A well-known shortcoming of vir- tually all electronic components is their sensitivity to temperature changes. It is true that triacs are not too bad in this respect, but they do not like low temperaturen: they fust stop working! This is caused by the fact that triacs require a higher gate current at low tempera- ture. Triacs are often triggered by opto-couplers which are not capable of supplying these higher currents. The circuit described, in contrast to "normal" triac triggers, contains an amplifier which ensures sufficient gate current under all tempera- ture conditions. The amplifier is formed by transistor IF=SmA IC1 -y TIL1,1 • Tri1 BC TIc 238B 206D Ti, which raises the signa) from the opto-coupler to more than adequate level. The use of capacitor C2 as a "dropping" reactance ensures that the dissipation in the drive circuit is virtually nu; jt also prevents the circuit presenting a dc load to the mains supply. The switch-o...