A DC power supply includes a point-of-load (PoL) regulator providing power to a load with a desired efficiency only when a PoL input voltage is in a first sub-range of a specified larger system input voltage range. The supply has an auxiliary circuit with an output in series with the supply input, generating an auxiliary voltage and adding it to the DC supply voltage to form a boosted supply voltage. Switching circuitry connects the supply input to the PoL input to apply a DC supply voltage as the PoL input voltage when the supply voltage is in the first sub-range, and connects the output of the auxiliary circuit to the PoL input to apply the boosted supply voltage as the PoL input voltage when the supply voltage is outside the first sub-range, maintaining the PoL input voltage within the first sub-range.