HIGH-PRESSURE DISCHARGE LAMP LIGHTING DEVICE, HIGH-PRESSURE DISCHARGE LAMP DEVICE USING SAME, PROJECTOR USING SAID HIGH-PRESSURE DISCHARGE LAMP DEVICE, AND HIGH-PRESSURE DISCHARGE LAMP LIGHTING METHOD

摘要

After the start-up operation of a high-pressure mercury lamp (4) has ended, the lamp current is controlled to a constant value to effect a transition to lighting using constant power. Except for a fixed period of time during which modulation is prohibited after the start-up operation has ended, frequency modulation control is performed such that the AC current frequency is modulated between at least a first frequency and a second frequency that is at a higher audible frequency than the first frequency. During the period from the end of the start-up operation to a prescribed time before the transition to constant-power lighting, the period from the end of the start-up operation to the point at which the transition to constant-power lighting occurs, or the period from the end of the start-up operation to a prescribed time after the transition to constant power lighting, which are set as periods of time during which modulation is prohibited, AC current at a third frequency, which is lower than that of the second frequency, is supplied without frequency modulation control. Quiet operation can be thereby improved without adversely affecting the AC current frequency modulation control for the purpose of appropriate growth and maintenance of the projecting portion of the electrode.