| 摘要 |
PURPOSE:To perform a soft start constantly evenin putting a power source off and then on immediately by discharging a charged electric charge of a time constant capacitor speedily through a discharge diode and a comparator means simultaneously as a power source gets off. CONSTITUTION:An error amplifier 19 for which a detection voltage of a discharge lamp terminal voltage detecting circuit is inputted into an inversion input end, with a reference voltage followed by a time constant of a capacitor 18 inputted to a non-inversion input end, and a diode 20 for transmitting an output of the error amplifier 19 to a voltage frequency converting circuit 9 only when a tube end detection voltage exceeds the reference voltage are provided, and a discharge diode 22 for connecting the anode side of the diode 20 which the non-inversion input end of the error amplifier 19 is provided. When a power switch SW is changed from on into off, a charged electric charge at the time constant capacitor 18 can be speedily discharged through the diode 20 and the error amplifier 19. A soft start can thus be achieved even when the power switch SW is put on immediately after that. |
