Patent ID: 7638987

Claim:
A power supply apparatus, comprising: a switching transistor configured to perform a switching operation for converting an input source voltage to an output power voltage according to a control signal; a transistor control circuit configured to generate said control signal based on a reference voltage and a feedback voltage proportional to said output power voltage; and a reference voltage generator configured to generate said reference voltage, to increase said reference voltage in a phased manner to increase said output power voltage in a phased manner to a desired value, and to decrease said reference voltage to decrease said output power voltage, wherein said reference voltage generator increases said reference voltage from a first voltage to a second voltage in a phased manner, and in each phase of the voltage increase between said first and second voltages, said reference voltage is held in the phase at a corresponding intermediate voltage which is greater than said first voltage and less than said second voltage, and wherein after said output power voltage reaches said desired value, said reference voltage generator decreases said reference voltage from said second voltage to said first voltage in a single step.