I understand the "full bridge", but that does not explain the 30V > 60V part.
A push-pull type is also fully-driven but with less components and has the double voltage part, eg. (just for the topology):
https://i.stack.imgur.com/h826H.png
A push-pull type is also fully-driven but with less components and has the double voltage part, eg. (just for the topology):
https://i.stack.imgur.com/h826H.png