Quote: Originally Posted by shotgunefx
But I don't think the diode wouldn't do anything but needlessly drop some voltage and prevent reverse current which should never happen in this particular situation.
I would just like to note that reverse current CAN flow through a regulator (at least the basic ones, like the 7812, fancier ones might not) I have made that mistake before. I connected a big capacitor AFTER a 5v regulator, thinking that even if the input voltage fell for a short time, the output should stay okay because if no reverse current flowed, the cap would maintain the output voltage for a short time. However, in practice, I discovered that is wrong... the voltage on the output drooped right with the input... I put a diode in series with the regulator input and everything was fine, since no reverse current could flow then.
Also, as people have been saying, find an LDO... you can find 1.5A and 3A LDO's relatively easily, for $1-2 and it will greatly improve your minimum input voltage. Add a schottky diode on the input and you should be good to go...