The attached Sync Buck simulation (schematic also attached), has non symmetrical AC current in the CST , but there is very little build up of magnetising current in the secondary of the CST, due to the use of the diode bridge at the CST secondary. Therefore, would you agree that this circuit is fine?
-The secondary magnetising current merely has a 2mA DC level in it. (its saturation level is 52mA).
In fact, even a unipolar CST setup is fine (with only single rectifier diode in the CST secondary), but just has up to 20mA DC level in the secondary magnetising current, which is unwanted, but doesn’t saturate the EP13 (3C96) core, which, with 50 turns, would need the secondary magnetising current to go up to 52mA before saturation was caused.
Anyway, in the attached simulation , the secondary magnetising current is seen by putting “I(L28) + I(L27)/50” into the waveform window.