DISCHARGE LAMP LIGHTING DEVICE

摘要

PROBLEM TO BE SOLVED: To transfer up to a relatively small electric power control condition at stable time from large electric power control at starting time by an extremely simple means. SOLUTION: A first lamp voltage detecting circuit 54 outputs a signal (i3 ) increasing as lamp voltage increases over a high area from a low area of lamp voltage of a discharge lamp 2. A second lamp voltage detecting circuit 56 outputs a signal (i6 ) which increases as the lamp voltage increases in a low area and maintains a constant value in a high area of the lamp voltage regardless of the lamp voltage. A resistance 145 outputs a signal (i4 ) according to a lamp electric current. A time constant circuit outputs a signal on which an increasing rate reduces as time passes. An error amplifying circuit 53 controls electric power to be supplied to the discharge lamp on the basis of an added value Vx of the respective signals (i3 , i4 and i6 ) or the like.