| 摘要 |
PURPOSE:To prevent a discharge lamp from being broken as a result of the attachment and removal work of the discharge lamp by including each filament on a common filament side of the discharge lamp in a starting circuit when two discharge lamps are to be lit with an automatic half bridge type inverter. CONSTITUTION:A starting circuit 25 is made to include the common filaments fb, fc of discharge lamps 5, 6. When the discharge lamps 5, 6 are installed under this condition, a condenser 27 is charged through a charge resistance 32, filaments fc, fb, and a charge resistance 26. When the charge voltage reaches the breakdown voltage of a start trigger element 30, the element 30 is turned, the charge in the condenser 27 flows to the base of a main transistor 9, and an inverter oscillates. If one of the discharge lamps is not present, the circuit 25 does not start. When one of the discharge lamp is to be replaced, the circuit 25 does not start if the lamp is inserted from the fa side. If the lamp is inserted from the fb side, although the circuit 25 is actuated, it does not oscillates because a resonance circuit of an inverter circuit 4 is not formed as the filament fa is not connected. |
