Other Parts Discussed in Thread: PMP9333,
Hi, my LM5116 based converter works amazingly well but I want to find out the load limits by calculating the junction temperatures of the most vulnerable components - they are MOSFETs and inductance. The main IC is surprisingly cool not effected by the load increase. Inductance temperature says all about it, so I see the MOSFETs are the weakest point. My schematic mostly follows PMP9333 reference design :
My design is different only due to input voltage is higher (84V) and to reduce turn-on ringing I use both HB resistor and HO high MOSFET gate resistor.
Junction temperature is calculated as Tj = Tc + (Kj x P)
where Tc is temperature measured at the top of MOSFET package, Kj is junction to top case coefficient , P - power dissipated inside the component . MOSFETs junction to top is known from datasheet - 18k/w ( I use Infineon BSC190N12NS3 )
How to find the individual component's dissipated power? Total power dissipated inside the converter 3.2W , efficiency 92% , how is this losses power distributed inside this design? Temperatures of both MOSFETs are equal which suggests that their power dissipation is about equal . If I know nothing better I can just assume that all the dissipation happens inside the MOSFETs but it is surely not true.