Over voltage crowbar - (for Mariss really )

Mariss,

I understand from one of your very informative posts, overvoltage is
a large cause of failure with Gecko stepper drivers.

Many years ago in the early days of semiconductors, the lab I worked
in developed a simple 'overvoltage crowbar' circuit that was desgined
to blow fuses if the rail went over a certain limit. Simplicity
itself, it consisted of a thyristor accross the supply, with a drive
circuit based on a zener diode, that turned the thyrisor on at a
certain voltage.

The theory was that fuses were not fast enough to protect the
semiconductors in the circuit, but the thyristor would drop the volts
and hold on long enough for the fuse to blow thus saving the day.

At the time we were protecting vastly expensive yttrium iron garnate
infra red multielement array detectors used to watch the Russians
from space, but could not a similar concept be incorporated to
protect Gecko 201 & 210's ?

Andrew Mawson
Bromley,
Kent,
UK