4kW LLC converter with split secondary windings?

[cupoftea]

Hi,
We are doing a Full Bridge LLC of 4kW , fsw ~ 100kHz, Vin = 400Vdc. Vout = +/-180Vdc
We are doing it as in the attached split secondary.
The thing is, we are sandwiching both secondaries between the two primary halves. But this then means that our two secondaries are not actually interleaved with each other, and so will not be well coupled….or the coupling to each from the primary may be different……do you think we will suffer this poor coupling sec to sec? I'd like to bifilar wind the secondaries, but since they are each made of multiple conductors, thats going to be difficult...also, there wont be enough bobbin depth for that kind of bifilar winding, on the EC70 bobbin.

 

[Velkarn]

we are sandwiching both secondaries between the two primary halves

as i understand, you construction is core-pri-sec-sec-pri, right?

what is the purpose of winding interleaving? for LLC leakage inductance is not issue, so why not pri-sec?

 

[cupoftea]

as i understand, you construction is core-pri-sec-sec-pri, right?

...At the moment, thats what we are about , yes....but we think the coupling between the secondaries wont be good enough......if the coupling between secondaries isnt good enough, there is big overvoltage spikes on the secondary diodes, which needs heavy snubbing