| 摘要 |
PROBLEM TO BE SOLVED: To perform power control of a discharge lamp in such a way that light flux of the discharge lamp becomes a rated light flux without complicating a circuit constitution. SOLUTION: A circuit 1 is provided with a power control means 5 which first performs supply of power exceeding a rated power to a discharge lamp 6, decreases the supply power to the discharge lamp next, and then performs constant power control to the discharge lamp 6 for lighting the discharge lamp 6 from a cold condition. A transition control means 8 for transition to the constant power control to the discharge lamp 6 after performing supply of power exceeding the rated power of it is composed to have plural time constant circuits of different time constants, or have a time constant circuit of an order number of two or more, and power control is performed to change a reduction rate of supply power to the discharge lamp 6 as time passes. |
