I’m trying to design a power supply for an electromagnet. For this, I’m using a Buck topologie in which the electromagnet is the coil. The voltage comes from a 400V PFC. Required current is 8 Amps (mean and rms).
So, I’m looking for a freewheeling diode rated 600V, 10A. I found such as VS-15EWX06FNTR-M3 (a bit overkill but OK).
Nonetheless, if I do the math about conduction losses :
Pcond = Vforw * Iaver = 1.5 * 8 = 12 W
Now, I’m not familiar with thermal problems but I’m not sure a DPAK package can endure that. So I checked the conductivity :
And it's about .... 70°C/W for junction to ambient ! That would raise the temperature over 700°C ..
So my question is : how can it be rated 15A ?! I understand that those figures are given for particular conditions like a case maintained at 25°C. But even with a perfect cooler, it seems impossible to me to dissipate like 22W in a diode with this package (or even more for higher ratings)
On the same hand, MOSFET rated 100Amps can have a RDSon about 0.1 Ohm which would lead to 1kW of dissipated power !!
Thank you for your help