Do coupled inductor sepic converter ringing currents cause zero hysteresis losses?

[Flyback]

Hello,
Do you agree that the huge 23Amp pk-to-pk circulating current in this sepic converter’s coupled inductor causes no hysteresis losses in the coupled inductor’s core?
So, -the following is a 7.5W coupled inductor sepic converter (Vin=5V, Vout=15V, f(sw)=104KHz, CCM).
Schematic (also pdf attached)
https://i40.tinypic.com/vfa2ht.jpg
The leakage inductance and the sepic capacitor have a resonant frequency of 104KHz, which is the same frequency as the switching frequency.
Due to this, there is an enormous , resonating, 23 Amp peak-to-peak circulating sinusoidal current which circulates through the coupled inductors and sepic capacitor.
However, would you agree, that this huge circulating current causes absolutely no hysteresis losses in the coupled inductor’s ferrite?, -and that this is because as it transitions through the primary, its magnetic field is oppositely polarised to the direction of the magnetic field that is produced as it travels through the secondary?
(in other words, the fields produced by this current cancel each other out, and so no hysteresis losses are produced.)?

 

[ronsimpson]

I have not made a resonant sepic converter. I have made sepic converters where I tried to keep the resonant frequency of the Ls and Cs much higher than the switching frequency.

I have also made a similar converter with a negative output.

I believe that there is energy stored on the inductors AND there is a transformer effect happening.
The energy stored in inductance will cause core loss.
The energy in the transformer effect (not counting leakage inductance) will do what transformers do. Like a forward converter using a transformer.
When you place voltage and time on a core you will get losses in the core.
Even if we can show no 'transformer' core loss, the leakage inductance is on the same core and it will cause losses.

I have not looked closely at one of these in a while.

 

[Flyback]

Thanks, though oft-times its difficult to get the L(leak), C(sepic) resonant frequency far above from the switching frequency, I mean , after all, the c(sepic) has to be big enough so that it has ripple voltage less than 5% of vin. Also, the leakage is likely to be at least 1% of the primary inductance....this tends to bring you in the range of the switching frequency.
The way round it is to add extra 'leakage inductance' by way of an extra inductor...however, this then gives us the problem of the resonance between this enhanced leakage and the c(sepic) coming in at a frequency which is too near to the feedback loop crossover frequency..this then needs an RC across the sepic capacitor to damp it.

Here is attached the ltspice sim