A power supply includes a power converter, a reference voltage generator, and a controller. During operation, the power converter produces an output voltage to power a load. The reference voltage generator (such as a voltage mode amplifier circuit) generates a floor reference voltage, a magnitude of which varies as a function of the output voltage. The controller compares an output voltage feedback signal (derived from the output voltage) to the floor reference voltage to produce control output to control timing of activating switches in the power converter to maintain the output voltage within a desired voltage range.