| 摘要 |
PURPOSE:To realize an electric power supply having a soft start function, by controlling a conduction time by use of a signal which is slowly varied after the electric power supply has been put to work, and a signal which is varied at every zero- cross point of an AC electric power supply, in a capacitor input type rectifying circuit. CONSTITUTION:Primary coil voltage v1 of an electric power supply transformer 2 at the time when an AC electric power supply 1 has been put to work becomes pulselike voltage gradually toward around a peak value from around a zero-cross point, and settles down in a stationary state. In case of a soft start operation, when AC voltage v0 rises from around the zero potential, and voltage vB of a capacitor 7H exceeds voltage vD of an inverted input of an operational amplifier 7D, a transistor 6E is held on while voltage is in a state of vC>VB>VD. When the voltage vB further rises and exceeds the voltage vC, the transistor 6E is turned off. Control after putting an AC electric power supply to work is executed by repeating said operation periodically. |
