ELECTRIC DISCHARGE LAMP LIGHTING EQUIPMENT

摘要

PROBLEM TO BE SOLVED: To prevent a non-lighting because of incorrect-detection of a voltage in a shape of a peak impressed to an electric discharge lamp at the time of low-temperature starting. SOLUTION: In the equipment which makes electric discharge lamp turn on with a half bridge inverter circuit of a self-excitation type driven by a voltage smoothed to flat in a manner of filling up a valley of a rectification output of an alternate current power supply, a frequency variable means to gradually reduce frequency from the frequency f1 at the time of preheating to the frequency f3 at the time of stable lighting through the frequency f2 at the time of starting is provided with by making a frequency of switching variable by restricting the drive signal of at least one of switching elements in a direction where ON time is shortened in the predetermined time after the power supply is turned on. And a protection means to restrict an output when a detected lamp voltage is higher than a predetermined value and also a means to stop operation of the above protection means substantially until it shifts from the frequency f2 at the time of starting to the frequency f3 at the time of stable lighting.