| 摘要 |
PURPOSE:To prevent the generation of an abnormal voltage when no negative charge is present in a pressure raising transformer by stopping to send out a pulse voltage of an oscillating circuit when the voltage applied to a resonance capacitor connected in series to a fluorescent tube is not detected. CONSTITUTION:When a luminous tube 14 has been taken out in the initial motion, the terminal TP1 of a wiring L1 is opened, where there is a possibility of generating an abnormal voltage in the terminal TP1. As no closed circuit sending a current to a resonance condenser C4 is formed in this case, the voltage generated on its both ends is 0V. Thus, the voltage given to the control input 121 of an oscillating circuit 12 from an oscillation control circuit 15 is rapidly changed from level H to level L. When the voltage of the input 121 of the circuit 12 is turned to level L, the circuit 12 stops to send a pulse output to a switching circuit 13, so that the switching motion of the circuit 13 is also stopped. Thus, the flow of electric current to the wiring L1 is eliminated, and the voltage of the terminal TP1 never exceed the voltage of the plus output 112 of a power source circuit 11. |
