ELECTRIC DISCHARGE LAMP LIGHTING DEVICE

PURPOSE:To obtain low luminous flux by detecting a current in an electric discharge lamp, and controlling an on-period of a switching element. CONSTITUTION:When a peak current of a lamp current 11a in an electric discharge lamp 1a tends to be voltage V0 or more of a power supply 2, an output of a comparator CP2 leads to an L level. Consequently, a capacitor C3 is discharged, to decrease reference voltage Vref, and a comparator CP1 is inverted to output an L level. Accordingly, a transistor Q1 is turned off to prevent a tube current from increasing in the electric discharge lamp 1a. In a period the peak current in the electric discharge lamp la is the voltage V0 or less of the power supply 2, the reference voltage Vref rises, and the transistor Q1 is actuated so as to maintain its on-operation till the peak current 1a in the electric discharge lamp 1a rises to V0. Thus by fixing a mean current of the electric discharge lamp, dimming can be stably performed without going out and a flicker to low luminous flux.