A control method improves the efficiency profile of a power supply across a wide range of output loading. The method includes obtaining a measure of output power for a power supply, which includes one or more output modules and an auxiliary power supply. The method determines whether a maximum power rating of the auxiliary power supply is sufficient to provide the measure of output power. Responsive to a determination that the maximum power rating of the auxiliary power supply is sufficient to provide the measure of output power, the controller of the power supply directs the auxiliary power supply to provide the output power.