Note that the paper you linked is still doing a two-step conversion - they essentially just removed the capacitors between the two steps. It doesn't do 48V -> 1

Note that the paper you linked is still doing a two-step conversion - they essentially just removed the capacitors between the two steps. It doesn't do 48V -> 1.5V, it does 48V -> 8V -> 1.5V. They even specifically point out the downsides of single-stage conversion topologies.