DISCHARGE LAMP LIGHTING DEVICE

摘要

PROBLEM TO BE SOLVED: To prevent a lamp life from being shortened and thermal stress from being applied to components due to overheating or excessive cooling of a filament of a discharge lamp, when discharge lamps of about the same outside form but different in rated output are connected together. SOLUTION: In a lamp-kind detecting circuit 5, a current detecting means 5a detects filament current If of a discharge lamp La and a voltage detecting means 5b detects filament voltage Vf of the discharge lamp La. A judging means 5c finds filament resistance from detected values of the filament current If and of the filament voltage Vf, and detects the kind of the discharge lamp La from the filament resistance. From a detected result of the lamp-kind detecting circuit 5, a control circuit 6 controls filament power supplied to the discharge lamp La into filament power necessary for the discharge lamp La connected to a ballast 1.