A system and method for closed-loop efficiency modulation for an AC/DC power system is provided. A boost-buck converter and a DC/DC converter connected in series receive a rectified DC feed signal from a AC input signal and deliver a modified DC output to an active load. A controller receives power data at various stages of the system and uses that data to modify a series of trim voltages provided to the feedback inputs of the respective converters to modify each converters output voltage. The controller modifies each converter's output voltage to maximize power efficiency while monitoring other data in the system to ensure the system is operating correctly and safely.