| 摘要 |
PURPOSE:To suppress the increase of loss and the heat rising in an inductor for resonance and a switching element by suppressing or stopping the switching operation of the switching element whenever a current flowing in the inductor for resonance exceeds a specified value. CONSTITUTION:A current flowing in an inductor for resonance 7 is constantly detected by a current detecting element 31. When a discharge lamp 9 gets to the state of half-wave discharge occurring in the end of life and the current flowing in the inductor for resonance 7 increases, the detected value detected by the current detecting element 31 exceeds a specified value. As a result, a judging circuit 32 judges it, and a controlling circuit 22 suppresses or stops the switching operation of a switching element 8 in accordance with the output of the judging circuit 32. Thus, the current flowing in the inductor for resonance 7 decreases so that the increase of loss and the heat rising in the inductor for resonance 7 and the switching element 8, which are caused by the deflected magnetic and the saturation of the inductor for resonance 7 occurring during half-wave discharge in the end of the life of a discharge lamp 9, can be suppressed. |
