| 摘要 |
<p>PURPOSE:To prevent generation of unstable lighting condition of light flux decrease and the like at the time of transition from an excessive lamp power supply condition upon start-up to normal lamp power supply condition, and enable function of rapid light flux rising restraining generation of excessive light flux just after lighting at the time of restart-up, with a simple configuration and low cost. CONSTITUTION:A control circuit CR2 is constituted in such a way that the excessive lamp power supply characteristic to a discharge lamp DL1 with respect to lamp voltage can be changed over to two kinds. The gradient degree of lamp voltage VDL at the initial stage of start-up of discharge lamp DL1 is detected, and according to the result, judgement of start-up and restart-up are made by a lamp condition detection circuit DT3 by which any one of two kinds of excesive lamp power supply characteristic is selected according thereto. With the constitution, it is possible to dispense with an auxiliary power source which supplies power to a circuit element for distinguishing the conditions of start-up and restart-up and make unnecessary the close arrangement of the circuit element to the discharge lamp, resulting in simple configuration and low price.</p> |
