please don't call that a buck converter
more like an upside down boost converter with the smoothing cap in the wrong place(b). Many of the topologies are electrical anagrams of sorts, but the terms have specific meanings. ref:
Regulator Topologies for Battery-Powered Systems - Tutorial - Maxim
also these and their right side up counterparts can all use a half bridge. The question is can they still with zvs/or zcs or whatever (though zvs needent be a requirement, only a lot of volts at 36kw is).