| 摘要 |
PURPOSE:To prevent the inflow of an over-current to the output side of a high frequency lighting circuit by connecting a filter circuit which has low impedance to high frequency waves and high impedance to low frequency waves to the output side of a high frequency lighting circuit in series. CONSTITUTION:On the output side of a oscillating transformer 4, a filter circuit 5 (for example condenser) which shows high impedance to commercial frequency and low impedance to high frequency is inserted between a secondary coil and an electric discharge lamp 10. Accordingly, when the electric discharge lamp 10 is lit, the electric discharge lamp 10 lights normally. And at that time, the filaments 11, 12 of the electric discharge lamp 10 is preheated as usual by the commercial frequency preheating voltage of a preheating transformer 20. Further, if both ends of the electric discharge lamp have short-circuited, an over-current tries to flow through the secondary coil of an oscillating transformer 4 by the commercial frequency preheating voltage of the preheating transformer 20, but the over-current is suppressed by the filter circuit 5. |
