I found this accidentally while searching for bridgeless PFC controllers (none found): Patent No.: US 7,915,874 B1 It is dated 2011 so you may have seen it before, but I hadn't.
Dr. Cuk discusses it in several videos on his site:
It is only fair to warn you that Dr. Cuk's ineptitude as a video technical presenter is only exceeded by his ineptitude as a salesman. He begins a sales pitch by insulting all possible customers, followed by irrelevant time wasting, hyperbole, and eventually some discussion of operation and advantages of his Cuk-buck2 topology. But they are better than a poke in the eye with a sharp stick, and anyone with an interest in power supplies should find the topology interesting.
Glen