DISCHARGE LAMP LIGHTING DEVICE

摘要

PURPOSE:To prevent a discharge lamp from flickering during the transient period such as the switching period when the discharge lamp is turned on or off. CONSTITUTION:The voltage of a DC power source E is converted into the high-frequency voltage by a self-excited externally-controlled inverter circuit 1, and a discharge lamp La is turned on with the high-frequency voltage. The on-state of a switching element Q1 is detected with the divided voltage of resistors R2, R3. An AND gate G1 prevents a switching element Q2 from being turned on during the on-period of the switching element Q1. A switch element SW3 suppresses the charging of a capacitor C when it detects that the on-period of the switching element Q1 is abnormally extended. The period when the output of an oscillator 2 can turn on the switching element Q2 is extended, and the switching element Q2 is surely turned on after the switching element Q1 is turned off during the transient period.