JPS6454698A - Lighting device for discharge lamp - Google Patents

Abstract

PURPOSE:To alleviate a load on a high frequency generator circuit and to secure a bright, safe condition at the time of replacing a discharge lamp by indicating an emissionless condition of one lamp during controlled lighting followed by the control of the high frequency generator circuit for maintaining lighting of each discharge lamp. CONSTITUTION:When one of discharge lamps l1, l2 deteriorates and becomes in a half-wave discharge condition during controlled lighting, a detection signal from an emissionless condition detection circuit 2 is counted with a counter 3 and a preheating timer circuit Tph is simultaneously reset. When preheating action and starting action are then performed and each discharge lamp is lit again, the preheating and starting actions are repeated. When the counted number reaches a specified value, only an output of an all light lighting oscillation circuit OSC2 for two lights is transmitted and thereafter the discharge lamps l1, l2 returns to an all light lighting condition after a preheating action.