I have been reading up on power supply switching and auctioneering diodes come up a lot as an alternative to relays. What I can't find on them is a circuit diagram. Does anyone have a schematic for an auctioneering diode? I would like to see how they work

 

Try the explanation at the link - http://www.amalgen.com.au/dc_power/auction_diode.asp

The diodes are external to both supplies.

 

As another example, you might see something like this in the schematic of a battery powered device that also has an aux DC power jack:

The diodes prevent the battery from being charged by the aux DC in, or discharged by the aux power if it's off.

 

Thanks guys that explains alot