A method for starting up a voltage-mode switching power supply into a biased load includes computing a ratio of the load voltage at the biased load to an input voltage of the switching power supply, generating a first signal indicative of the duty cycle of the voltage-mode switching power supply, comparing the first signal indicative of the duty cycle to the ratio, and turning on an output stage of the voltage-mode switching power supply only when the first signal indicative of the duty cycle is equal to the ratio. In this manner, the voltage-mode switching power supply can be started up to supply power to a biased load without dragging down the load voltage of the biased load.