| 摘要 |
PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device that can steadily detect no-load state such as breakage of filament and dislocation of filament with a simple circuit structure. SOLUTION: The inverter circuit 1 converts the DC voltage of the DC power source E1 into a high frequency AC voltage and supplies to the discharge lamp La. The filament detecting part 3 comprises a series charging circuit 7 that is composed of resistors R1, R2 connected in series between the both ends of the second DC power source E2 and a charging capacitor 3, a diode D1 that is connected between the connecting point of the resistors R1, R2 and the connecting point of a filament f1 and capacitor C2 of the discharge lamp La, with its anode on the connecting point side of the resisters R1, R2, and a level detecting circuit 8 that detects the both ends voltage of the charging capacitor C3, and judges as no-load state when the both ends voltage of the charging capacitor C3 surpasses a prescribed threshold voltage, and the output control part 6 stops the oscillating action of the inverter circuit 1 based on the judgement result. |
