| 摘要 |
PURPOSE:To restart oscillation of an inverter immediately after a load abnormal state is canceled by shortcircuiting both ends of the switching element of a holding circuit according to the detection outputs of a circuit for detecting the cut-off of a DC power source. CONSTITUTION:When abnormal lamp voltage is detected by an abnormality detection circuit 17, an oscillation stopping circuit 12 and a holding circuit 14 operate and the output of a base current source is indirectly released and oscillation of switching transistors 5, 6 is stopped and this oscillation stopped state is held by the holding circuit 14 for the duration of power supply. When the power is turned off for the replacement of lamps, the divided voltage of a voltage dividing circuit 18 is lowered and a reset circuit 19 operates and both ends of the holding circuit 14 are shortcircuited. With this constitution, when the power is turned on after the replacement of lamps, oscillation is immediately restarted and a discharge lamp 15 can be lighted and the not-turn- on of the discharge lamp 15 due to the influence of residual charge remaining in the switching element of the holding circuit 14 after the power is on, can be prevented. |
