Is DC transformer possible ?

Yes, stepping up/down of DC is possible, but not with the conventional transformer(winding transformer). Transformers in the world of DC are known as Choppers. Boost chopper is used to step up and buck chopper is used to step down DC.

Interestingly as we can perform step up/down in a particular AC transformer by altering the input connections with the output connections. In DC we have buck-boost chopper to do both the things with removing connections.

#THEWATT