Regarding the MOSFET LOSS

Hello Sudeep,

The purpose of the TI E2E forums is to support our customers having issues with TI components.  This sort of open-ended question unrelated to any particular IC is too general to be adequately addressed.  MOSFET losses depend heavily upon the topology and condition in which they are used.  Even a "flyback converter" can be subdivided into isolated, non-isolated, CCM, DCM, and QR, with different aspects of losses pertaining to each.  The following paper gives a good overview of conduction and switching losses, although it does not specifically address the flyback topology.  Portions of the general equations can be adjusted based on conditions, such as turn-on current and reverse recovery current can be set to zero in a DCM flyback topology, but not in a CCM application.  MOSFET Power Loss Calculations (Infineon).pdf

Searching the world-wide-web with a search engine will bring up numerous papers and sites, many with different equations as you mention. The differences are most likely the result of the topology and operating conditions in which the MOSFET is used.  You'll need to find an App-Note closest to your application.  Most of the time, these equations tend to give conservative results, that is, they predict higher losses than actual.  This means that you are unlikely to develop any overheating situation if you design with those results.  Of course, some engineering judgment is necessary to discard results that obviously don't make any sense or are grossly overstated.   Guidelines from a reputable MOSFET manufacturer are likely to be close enough to reality to obtain reasonable results.

Regards,
Ulrich