Electronic – Cuk topology patent

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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.

EDIT:

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".

Best Answer

Disclaimer: I am not a lawyer and patent law is complicated, especially because it differs greatly between jurisdictions.

The patents you linked to have long expired. This means you can duplicate the converters covered in the patent. After all, that’s the point of patents. The inventor discloses the invention in return for a 20 year monopoly right. After the end of the 20 years everyone can use the invention.

If you find any new patents, they will cover only improvements that have not been disclosed in the prior art (old patents). Read the claims of the patent. They limit what is protected. For example, suppose there is some new capacitor X that improves the performance of buck converters. A claim will look like this:

  1. A buck converter comprising at least one capacitor X.

According to the above claim you can still use buck converters, if you do not include capacitor X.

What can happen if you infringe on a patent is that the assignee (owner of the property rights) can ask you to stop selling, using, manufacturing, or importing the invention. If you refuse, they can get a court order for the same.

Keep in mind that patents are regional rights. The only patents valid in your jurisdiction are the patents issued by your local patent office.

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