Here’s an app note from Maxim describing how to calculate power dissipation of MOSFETs used in high-power switching supplies. The article is focused on CPU power supplies which operate at lower voltages (0.9-1.75v) but require loads of current (+60A).
This article provides step-by-step instructions for calculating the power dissipation of these MOSFETs and determining the temperature at which they operate. It then illustrates these concepts by stepping through the design of one 30A phase of a multiphase, synchronous-rectified, step-down CPU core supply.
Mmmm… I’ve been toying with the idea of making a 0-3 volt, 100 amp current limited supply suitable for driving 808 nm FAP laser arrays like this http://r.ebay.com/Bf4Q3c but it will probably never happen. But its fun to dream and plan.
Making spike/glitch free power supplies with this kind of current isn’t the easiest thing and the these lasers self destructs almost if you just look the wrong way at them. :)