I want to use as a starting point for this discussion the article A35 in the design center. This article shows how the size of converter shrinks, and its efficiency goes up, if you eliminate the need to regulate. The converter only isolates. Storage elements virtually disappear, and resonant transition switching can be naturally achieved.
High Efficiency Converters - Next Generation
Vicor led the way on this with their converters which give 95% efficiency and amazing density. Synquor also did their isolation with a simple push-pull, no exotic resonant conversion, and IR had a demo kit with a half bridge, also achieving 95%. Again, no resonance, just soft transitions.
Now, I see publications coming out with promised efficiencies of 99%. Remember, we are talking high voltage input converters, not little point of load bucks. I'm not sure I believe it, but there again we never believed Vicor could do his converter either, 5 years before it came out.
What is the truth? And what is the role of the LLC converter moving forward? It is claimed the LLC is part of the picture to get to even higher levels, but is that true?
When I was at Virginia Tech, we found there was no magic to resonant converters. The switching loss of regular converters was replaced with losses in the added passive components, and it was a struggle to come out ahead. Resonant inductors were especially challenging with proximity losses causing a lot of problems.
So, two questions:
What are the real numbers that people are seeing for next generation efficiencies? Real-world products, please, not simulations or calculations.
And, is LLC needed to get there?