I'm designing a high-power LLC converter. For the transformer design, I've come up with a 16-to-1 turns ratio.
The design is size-limited so I'm not free to select a core with any shape or dimension. Due to this limitation, I picked up a core that seems to fit mechanically (but it isn't a good fit for that application), and wound 32 turns for primary and 2+2 turns for centre-tapped secondary. Surprisingly, the windings fitted quite nicely, and the calculated losses seem acceptable. But the transformer occupied quite a hell of a height so the air coming from the fan will be blocked almost completely by the transformer and thus will not reach the secondary-side components.
Now I and my colleague are thinking about stacking a standard shape but smaller core to make a planar-like transformer having less height but more length. The problem with this idea is that the copper losses will skyrocket due to the increased mean length of a turn.
So I'm thinking about halving the number of turns since I'll have a larger Ae.
And here's the question: The secondary will have only one turn. Is it a good idea? Will it bring any distinctive problems?
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I'm pretty sure that the leakage percentage will be high for a single-turn secondary because
- The primary will take most likely only one layer so the benefit of the interleaved primary will be lost, and
- The single turn will not be spread across the window so the coupling factor will be lower.
So I think I shouldn't expect a good voltage regulation because I will have to switch to the integrated resonant choke option (initial design involves a separate resonant choke) due to the space constraints so the tank and thus the operating point will change too much.
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PS: Sorry for the wall of text. I did try my best to give as much detail as possible.