Dual voltage input with Schottky Diodes

Thread Starter

bigjoncoop

Joined Feb 1, 2019
173
ive used Schottky Diodes before for dual inputs before but im wondering if the "switch" is immediate? Trying to provide power to a gps module until it gets a gps lock then power up rest of system without the gps module "rebooting"...

here's the circuit:

DUAL INPUT.JPG
 

DickCappels

Joined Aug 21, 2008
8,714
That looks like a good solution.

There will be a brief period of overlap of conduction as the input to one anode drops below that of the other, but that is a good thing. There should be no dropout of power to the GPS module. I have used that method several times, getting into a complicated switch-over circuit is not worth it to save a few hundred millivolts, at least in my applications.

You may want to raise the flight controller's 5V supply or lower the battery backup voltage by a hundred millivolts or two and keep the diodes in thermal contact with one-another to assure that no significant current is drawn from the battery. Alternatively use a Schottky for the flight controller 5V connection and silicon junction diode for the backup supply.
 
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