I working on loss modelling of PFC converter. My PFC operates in boundary conduction mode (CrCM) and the MOSFET switches on at Valley or zero valley (ZVS) of drain-source voltage. In order to achieve VS/ZVS, I used a parallel capacitance (22pF from datasheet) and reverse diode (Body diode) across the MOSFET. To calculate the power loss I am using thermal model. The problem is, at the valley point (when let's say Vds = 320V) the instantaneous voltage drop across capacitor causes a big current spike (approx. 900A) through the MOSFET. Thermal model calculates conduction power loss corresponding to this current spike too which is in order of kW. Is there any way around to get an accurate power loss during soft switching?