[sdiy] PSU question.

[mirwin at qouest.net]

The modules that the regulator is supplying power to have each their own
bypass caps (electrolytic and ceramic)... with several modules
connected, this can add up to a fairly large capacitance. The diode
prevents this distributed capacitance from discharging into the
regulator output in the event that the regulator suddenly sees no input
(unit unplugged from wall, wallwart unplugged, power failure). If the
electrolytic cap on the input side of the regulator is sufficiently
large to provide a "slow shutdown" this should be no problem. If the
regulator is being powered by a DC-output wallwart (and the
main filtering electrolytic is inside the wallwart, rather than
directly beside the regulator chip), then damage could occur if the
wallwart is unplugged, or the regulator input is momentarily shorted,
and the protection diode is not present.
Regards, Mike