| 摘要 |
PURPOSE: To carry out an optimum control by surely detecting the installing and the noninstalling of a discharge lamp and a burnout of a filament. CONSTITUTION: A DC power feeding from a DC power source 1 is converted into a high-frequency AC power by an inverter circuit 2 and it is fed to a discharge lamp La. To the filament at the (a) side of the discharge lamp La, a noload detecting circuit 10 is connected through a resistance R103 . The noload circuit 10 turns on and off transistors Q101 , and Q102 by the current flowing to a DC current loop formed by including a pair of filaments of the discharge lamp La. Consequently, since the DC current loop is cut off in the noload condition to turn off the transistors Q101 and Q102 , a control power source Vcc is not fed to an exciting circuit 8 to operate the inverter circuit 2. As a result, the inverter circuit 2 is stopped and the application of a high voltage in the noload condition can be prevented. |
