| 摘要 |
PURPOSE:To prevent an overcurrent flowing at the start of an electric discharge by by-passing and attenuating the current of a current limiting circuit with a control signal via a switching action when the overcurrent is detected. CONSTITUTION:When an overcurrent flows in a circuit at the start of the electric discharge of a discharge lamp 8, the overcurrent control signal generation section lid of a current limiting circuit 11 generates an overcurrent control signal and applies it to a switching element 11a to turn it off. The current flowing in a choke coil 11b flows through a diode 11c and is attenuated. When the current flowing in the choke coil 11b is reduced to a prescribed value or below, a comparator 11e outputs a control signal to turn the switching element 11a on. The current flowing in the discharge lamp 8 is controlled within the prescribed upper limit and lower limit for normal operation, and the overcurrent is prevented from flowing. |
