| 摘要 |
PURPOSE:To obtain stable lighting even in connection to a phase control light adjustor by setting a running angle of the phase control light adjustor for starting initial operation larger than that for lighting off a discharge lamp after lighted on. CONSTITUTION:AC voltage which has a running angle controlled from an AC power supply 1 via a phase control light adjustor 2 is input to a full-wave rectifier 3. If a running angle of the light adjustor 2, obtained in a running angle detecting circuit 7, is larger than 90 deg., a switch element 11 is open-close- controlled through a control circuit 8 to perform pre-heating of filaments 16, 17 for a discharge lamp 15 and also to light the discharge lamp 15. When the discharge lamp 15 is lighted, a load condition in view of the light adjustor 2 is changed to affect the running angle as well, which is narrower than that before lighted. As a result, the drive of the element 11 is stopped and the running angle for lighting off the discharge lamp 15 is set smaller than that for starting the discharge lamp 15, thereby to allow it to be lighted off again even if the running angle is narrow when lighted on and to be stably lighted. |
