IT’S no secret that power converters increasingly emphasize energy efficiency. For example, 115-Vac computer power supplies must exhibit a 94% energy efficiency at 50% of their rated load to receive an 80 Plus Titanium rating; 230-Vac supplies must hit 96% at half their rated load to get the designation. For external power supplies (as used by laptops, tablets, and so forth), the Dept. of Energy recently came out with Level VI energy efficiency standards mandating active-mode efficiencies in the 86 to 88% range from most output powers.

A generally understood maxim is that for power supplies to get denser, they must also get more efficient. That works up to a point. Then you reach a point where incremental increases in efficiency come only at great cost and effort, or alternately, you must give relief on one to get the other.