Patent ID: 7215108

Claim:
A method for starting up a voltage-mode switching power supply, the voltage-mode switching power supply receiving an input voltage and providing a regulated DC output voltage at a DC output voltage terminal, the voltage-mode switching power supply being operated to provide a final DC output voltage having a first value, the DC output voltage terminal being coupled to a load wherein the load is biased to a load voltage having a second value greater than zero and less than the first value, the method comprising: computing a ratio of the load voltage having the second value to the input voltage; 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, the output stage generating a second signal having an average value corresponding to the DC output voltage at the DC output voltage terminal.