| 摘要 |
PURPOSE:To achieve the extension of life and miniaturization of a circuit by providing a timer circuit for short-circuiting between the base of a transistor and an emitter for a fixed time after inputting a DC power source. CONSTITUTION:When a DC power source 1 is inputted, an oscillation circuit 2 starts to operate, a transistor(TR) 6 is switched, a voltage is generated in the secondary winding of an oscillation transformer 4, and the both filaments of a discharge lamp 32 are preheated. At the same time, as timer circuits 19 and 11 also start to operate and output at high level, the power source voltage of the oscillation circuit 15 is short-circuited by a TR 13 and does not operate, and the base electric potentials of TRs 27, 28 are short-circuited by a TR 21 to stop oscillation, so that the lamp is in the preheating state during this period. Then, the output of the timer circuit 19 is reduced from high to low level while the timer circuit 11 maintains the high level, and a 100% lighting is conducted. Then, the output of the timer circuit 11 is reduced from high to low level while the timer circuit 19 maintains the low level, and a light-control lighting is conducted. Hence, the life can be extended. |
