How to do redundancy for a DC/DC converter? So that if one of the converters fails the other gets switched on
Redundant systems would typically employ an ORing-FET as shown below (source):
The idea is that redundant DC-DC converters supply the required voltage in a current sharing configuration so that both converters supply equal current and therefore have (pretty much) equal thermal stress.
In a fault situation the ORing FET isolates the problematic converter and the other one takes over.