GLOW-STARTING DEVICE FOR DISCHARGE LAMP

摘要

PROBLEM TO BE SOLVED: To maintain light output of a discharge lamp as much as possible even when an emitter is exhausted. SOLUTION: A power conversion part PC alternately impresses a discharge lamp La with voltages having lower amplitude and higher amplitude than that of characteristic voltage defined by the characteristic of lamp current-lamp voltage according to glowing conditions of the discharge lamp La. The lamp voltage is detected by a voltage detecting circuit VS, and the lamp current is detected by a current detecting circuit IS, thus an exhaustive degree of an emitter of the discharge lamp La is detected. A control part CN controls the output voltage of the power conversion part PC so as to keep the light output of the discharge lamp La nearly equal to that of normal time according to the exhaustive degree of the emitter.