Smps Ferrites, Frequency and Loss

Ugh...I have to change a non-isolated 700khz Cuk converter into an
isolated version.
Safety reasons.
Currently, the power inductors feel like 30C. Nice @~100W transfer.

I suspect, popping in an isolation transformer running at 700khz will
create a humongous drop in efficiency.

Transformer Stresses
Vprimary: 111Vrms (square wave, D~40%)
Iprimary: Positive peak: 0.7Amps, Negative peak: -1.2Amps
f: 700khz
Lp: 300uH and up
N ratio: 1:1
=one big ass hot ferrite transformer?

I'm trying to figure out the 'sweet spot' for the smallest transformer
size for a 20C temp rise.
I'm too newbie at magnetics for smps design. Should I drop f to 100khz
and redesign?

Or get crazy and make f higher and use an air core transformer.
But there's the crappy coupling of ~0.5, emissions and wire losses.


D from BC
British Columbia
Canada.
.

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