Patent ID: 7724544

Claim:
An AC power supply apparatus, comprising: an input device to perform on/off control of a DC power supply in a unit time on an amount of current caused to flow through a load, the amount of current includes a first predetermined amount of current and a second predetermined amount of current; an oscillation device to provide oscillation at a high AC frequency in an energized period of the DC power supply in a case where the amount of current to the load is set to the first predetermined amount of current and to provide oscillation at a low AC frequency in an energized period of the DC power supply in a case where the amount of current to the load is set to the second predetermined amount of current; and an output device of a high voltage to boost output of the oscillation device and to supply the boosted output to the load; and wherein when a light modulation level of the load corresponding to the second predetermined amount of the supplied amount of current is set in advance and the light modulation level is reached, an oscillate instruction is issued to the oscillation device.