19 Jan
2010
19 Jan
'10
4:39 p.m.
Chuck Guzis wrote:
But I thought part of the problem was that the regulator with the
slightly higher output voltage would drive the voltage difference
against the output of the lower-voltage regulator? Wouldn't isolation
diodes prevent that from happening?
Peace... Sridhar
Couldn't
you get around at least part of the problem with isolation
diodes?
No sir. Consider that the output of one 7805 might be 5.05 volts and
of the other, 4.95 (manufacturing tolerances being what they are,
that's not unreasonable). The bulk of the current will be conducted
by the 7805 with the higher voltage output. One might put a resistor
in series with the output of each one to balance the load a bit, but
that would play hob with the voltage regulation. (On the other hand,
this technique is used when paralleling rectifiers to balance the
current.)