| 摘要 |
PROBLEM TO BE SOLVED: To determine a life of a discharge lamp before its lighting is started. SOLUTION: This discharge lamp lighting device is provided with the discharge lamp 1 lightedly controlled by a lighting control circuit 2, a current detecting means 10 to detect a current passing through the filament electrodes of the discharge lamp, a voltage detecting means 11 to detect a voltage between the filament electrodes, an A/D converting means 12 to digitally convert a detected value from each detecting means, a memory 15, and a CPU 13 to drivingly control the lighting circuit. The CPU computes a filament resistance value Rc by taking in the detected values of the voltage and the current from the A/D converting means right after starting preheating control to store it in the memory. After that, the detected values of the voltage and the current are taken in for every fixed time to compute the filament resistance value Rh, and its ratio Rh/Rc to the resistance value Rc is found. When the time required before the ratio Rh/Rc reaches a prescribed value (a) becomes the allowable minimum preheating time or less, the discharge lamp is determined to be in the last stage of its life. COPYRIGHT: (C)2004,JPO&NCIPI |
