22 Jul
2011
22 Jul
'11
3:34 p.m.
Thinking about it some more, I guess it makes sense to
crowbar the output
that is rising and going to cause damage rather than to crowbar something
nearer the input and maybe end up having to wait longer for reservoir
capacitors to discharge before the output voltage drops, even if there may
be more damage in the power supply in some cases.
It depends. I'v ecertainyl seen linear PSUs where the crowbar SCR is
conencted acros the smoothing capacitor on the input side of the
regualtors (of course it's trigged by an overvoltage on the output line).
And it's common in alrge SMPSUs for the crowabar SCR to be on one of the
'lesser' outputs. It'll shut the supply down just ans well as if it were
on the main output and it doens't have to handle as much current.
But yes, in gnral, crowbars operate on the principle that the PSU needs
repairing anyway, and a little more damage isn't too seruous, wherehas
having to replace large numbers of logic chips is.
-tony