19 Jan
2010
19 Jan
'10
1:27 p.m.
On 19 Jan 2010 at 16:10, Sridhar Ayengar wrote:
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.)
But, as someone mentioned, the bigger problem is that linear
regulators tend to dissipate a lot of heat, especially when the input
voltage is substantially higher than the otuput voltage.
Better to use a buck regulator in this application, methinks, and
save some watts.
--Chuck