| 摘要 |
PURPOSE:To confirm abnormality of a discharge lamp based on a burning condition of the discharge lamp, and to lower the temperature of a pipe wall, so as to facilitate exchange work of the discharge lamp by providing a control means by which current running in a filament on the side of half wave discharge is controlled when the discharge lamp falls into a half discharge condition. CONSTITUTION:A control means is provided that is composed of switches SW1, SW2 connected with each other in parallel between both terminals of filaments F1, F2 of a discharge lamp FL, and of a half wave discharge condition detecting part 21 that detects a half wave discharge condition of the discharge lamp FL and turns the corresponding switches SW1, SW2 ON. When it falls into a half wave discharge condition, the switches SW1, SW2 on the emitter-less side short-circuit between the respective filaments F1, F2, whereby current running through a condenser C0 hardly runs in the side of filaments F1, F2, and the generation of extreme temperature rising is prevented beforehand. |
