| 摘要 |
PURPOSE:To facilitate setting for operating a clamp circuit normally in the case an input voltage of an inverter circuit is different. CONSTITUTION:A voltage of a DC power supply is voltage converted by a chopper circuit 2, and its output is smoothed by a smoothing capacitor C00. This smoothed-output is converted into a high frequency voltage by an inverter circuit 1 to light a discharge lamp La by high frequency. To an output of the inverter circuit 1, a resonance circuit comprising a current limiting inductor L0 and a preheating capacitor C1 is connected as well as the discharge lamp La. A clamp circuit 3 is provided in which an input voltage to the inverter circuit 1 is restricted almost at a voltage in normal condition of the discharge lamp by using a voltage of the resonance circuit at the time of an abnormal lighting of the discharge lamp La. By providing a chopper circuit 2 for voltage conversion of the DC power supply, the input voltage to the inverter circuit 1 can be regulated to be such a voltage as to actuate the clamp circuit 3 normally. |
