In Reply to: Inverse parallel SCR drive question posted by Jeffrey Dinkmeier on 05/09/00 at 9:07 PM:
It may be that the schematic has been simplified for the sake of clarity, but if not, then I'd have two comments about the deisgn.
1) When the "fan only switch" is open, the two SCR gates have no leakage suppression provisions. That suggests the possibility of unintended triggering.
2) Wnen the "fan only switch" is closed, trigger current for the gate of one SCR has to come from reverse breakdown of the gate of the other SCR. That I do NOT like!
John Dunn - President