Patent ID: 7129681

Claim:
A power supply apparatus, comprising: a switching regulator which performs start and stop operations in response to a first control signal and generates a first constant voltage in response to a first voltage switching signal to output the first constant voltage as a first output voltage; a series regulator which performs start and stop operations in response to a second control signal and generates a second constant voltage in response to a second voltage switching signal to output the second constant voltage as a second output voltage; and a controller which generates the first and second control signals and the first and second voltage switching signals, controls the switching regulator and the series regulator to simultaneously operate for at least a predetermined time period to lower a voltage level of the first output voltage using the first and second control signals, respectively, and controls the switching regulator and the series regulator such that the first output voltage of the switching regulator is greater than the second output voltage of the series regulator using the first and second voltage switching signals.