Fan Speed Control is Cool! - Maxim   [Open results in new window]
... The one exception, however, is that DC-DCs are ideally 100% efficient and don't
generate any heat (real-world efficiencies tend to be around 75% to 95%). ...
korea.maxim-ic.com/appnotes.cfm/an_pk/1784/ - 52k

Fan Speed Control is Cool! - Maxim   [Open results in new window]
... The one exception, however, is that DC-DCs are ideally 100% efficient and don't
generate any heat (real-world efficiencies tend to be around 75% to 95%). ...
korea.maxim-ic.com/appnotes.cfm/an_pk/1784 - 52k