| 摘要 |
PURPOSE:To ignite a discharge lamp with nearly the fixed voltage and lower the withstand voltage of a socket for discharge lamp by providing a voltage control device changing the voltage across the first capacitor at the pulse generation phase in response to the output voltage fluctuation of a rectangular-wave power source. CONSTITUTION:A serial circuit of a resistor 8 and a switch element 9 is connected in parallel with a capacitor 3 to control the voltage V3 across the first capacitor 3 in response to the fluctuation of the voltage V1 in the period from the polarity reversal of the output voltage V1 of a rectangular-wave power source 1 to the high-voltage pulse generation phase. When the voltage V1 is increased to the preset value or higher, the switch element 9 is excited at least in the period from the polarity reversal of the output voltage V1 of the power source 1 until a bidirectional thyristor 4 is turned on and the high-voltage pulse voltage V5 is generated on the secondary winding 5b of a pulse transformer. A discharge lamp is thereby lit with nearly the fixed voltage, the excessive rise of the high-voltage pulse voltage is prevented when the power source voltage is increased, thus the withstand voltage of a discharge lamp socket can be lowered. |
