| 摘要 |
PURPOSE:To prevent flickering of light and generation of a flash at starting time by smoothly raising a light dimming level from a minimum light dimming level transferred to a predetermined light dimming level after applying a starting pulse. CONSTITUTION:An external signal of light dimming of variable period fixed on-time tau is input between terminals alpha, beta. In the period, a photocoupler PC is actuated to turn off transistors Q10, Q11, and a capacitor C12 is charged with divided voltage of resistors R37, R38 through a resistor R35. This voltage is set to a minimum light dimming level and supplied to an emitter of a transistor Q8 through a gate circuit G2. Next in the period except tau, the transistors Q10, Q11 are turned on, and when middle point voltage of resistors R31, R32 is set higher than the middle point voltage of the resistors R37, R38, the capacitor C12 is charged with voltage higher than when the transistor Q11 is turned off. In this way, flickering of light and generation of a flash are prevented. |
