While searching for a good inverting SMPS topology, I stumbled across the Cuk topology which suits me perfectly by all means. The only thing that worries me is that unlike more common SMPS topologies, like inverting buck-boost or flyback, Cuk topology seems to patented according to wikipedia and many other sources.
I am going to use the Cuk topology in a PSU for a eurorack synth I am working on and I was thinking about selling some PSUs made from leftover PCBs and parts.
So, my question is: realistically speaking, how safe is it to use the Cuk topology in commercial products today? What could be the effects of doing it? Both in case of niche, yet still commercial products and in case of more spreaded ones.
The wikipedia gives links to expired patents.
I am, however, pretty much sure that a number of other patents with slight changes could also be filed in more recent years (especially from IC manufacturers), but wasn't able to find any.
I am planning to sell the product mostly in Russian Federation, the patents are from the US. But still, theoretically speaking, what could happen in case if the product well be sold with worldwide shipping?
I do understand that this is more of a "lawyer" question than "electrical engineering" one, so the "electrical engineering" part of the question is "how do engineers deal with it".