| 摘要 |
PURPOSE:To provide a stable light output having no flicker by setting the ON-time of a control signal for lighting an electrodeless discharge lamp longer than the time obtained by adding the time until the discharge lamp is lighted and the time until high frequency power is stabilized after lighting. CONSTITUTION:The ON-time (lighting time for lighting an electrode less discharge lamp 7) of a dimming signal given from a control signal generator 9 to a dimming circuit 6 is set longer than the time obtained by adding the ignition starting time of the discharge lamp 7 and the time until the output of high frequency power is stabilized after lighting. Thus, the fluctuation of the ignition starting time is absorbed, and even in the state where the light output is throttled by time division control, a substantially fixed light output can be provided although it is slightly fluctuated every period. Namely, even when the duty ratio of time division at the flashing or dimming of the discharge lamp is small, the lower limit lighting time can be kept for a required time for lighting or more, the light output having no flicker can be consequently provided, and the dimming-allowable lower limit can be minimized. |
