| 摘要 |
PROBLEM TO BE SOLVED: To provide a lighting device capable of resolving failure due to repeated lighting and extinction in a light source at deep dimming. SOLUTION: An electric discharge lamp FL is lit, by oscillating field-effect transistors Q1, Q2 in an inverter circuit 12. A detecting circuit 27 detects the lighting conditions of the electric discharge lamp FL. A control circuit 16 controls the field-effect transistors Q1, Q2 in a feedback mode, based on the load current of the electric discharge lamp FL detected by the detecting circuit 27. The control circuit 16 dims the electric discharge lamp FL for lighting by relatively changing an oscillating period and an oscillation-stopping period during one cycle of switching control for controlling the oscillation of the field-effect transistors Q1, Q2 in the inverter circuit 12. When the load current of the electric discharge lamp FL reaches a predetermined threshold value during the oscillation-stopping period, the oscillation-stopping period is terminated to start the oscillation of the field-effect transistors Q1, Q2; and the threshold is set, at a level higher than the region indicating the extinction of the electric discharge lamp FL. COPYRIGHT: (C)2011,JPO&INPIT |
