| 摘要 |
PURPOSE:To obtain the stable operation of an inverter even at the final stage of the life of a discharge lamp by detecting the voltage across both ends of the discharge lamp, and stopping or reducing the output of the inverter when the detected output rises. CONSTITUTION:When half-wave discharging occurs at the final stage of the life of a discharge lamp 3, a DC current flows in the lamp current flow path of the discharge lamp 3, the DC current is blocked by capacitors 6 and 7, a current transformer 5 is not polarized via a damper resistor 8, and a transistor inverter 1 is stably self-excited. The terminal voltage of capacitors 6 and 7 is detected by a control circuit 20, if the detected output rises, the inverter output is stopped or reduced. The polarization of the current transformer 5 is prevented when half-wave discharging occurs at the final stage of the life of the discharge lamp 3, the inverter 1 is stably operated, and the detected voltage of a safety circuit is not affected by the dispersion of the lamp voltage. |
