mdocod, your observations are well thought out but you've made a mistake. The +5V and +3.3V loads are not subtracted from the labeled +12V rating. It is is assumed that the +12V has the additional capacity to take the load from the +5V and +3.3V as well as its native load. And conversion efficiency doesn't come into at all in any way. The +12V load in a DC-DC PSU is essentially labeled wattage divided by 12 and rounded. That is all. It's sometimes labeled lower, but for unfathomable reasons, perhaps just because the product manager in charge did not understand how DC-DC PSUs work. There are people in the industry who aren't very good at their jobs, you know.
post #41 of 46
10/4/12 at 8:50pm