| 摘要 |
PROBLEM TO BE SOLVED: To prevent excessive power from being supplied even while a discharge lamp is lit in control of constant power by switching the control so as to reduce the lamp current supplied to the discharge lamp to a value not more than a predetermined one when the lamp voltage exceeds a rated voltage range. SOLUTION: At the initial stage of lighting, an igniter circuit 5 operates based on high voltage as much as 400 V, and this voltage is boosted up to 20 kV and is fed to a discharge lamp 14 in an insulated situation. As a result, the voltage of 20 kV is applied to two electrodes of the discharge lamp 4 and the movement of ions are started between the electrodes. The discharge lamp 4 starts to emit light by the aid of the movement of ions and gas. In an electrode activation process step, a central processing device 18 switches a bridge control signal so as to operate transistors 13, 14 of a diode bridge, and each of the electrodes is brought into a state to generate ions easily. Thereafter, constant power is continuously supplied to the discharge lamp 4. |
