POWER FACTOR IMPROVING RECTIFIER CIRCUIT

摘要

PROBLEM TO BE SOLVED: To prevent overshoot voltage appearing just after the power is turned on by means of a small-size load comprising only a few components by installing an overvoltage protective circuit for suppressing excessive rectified and smoothed voltage in parallel with a rectifying and smoothing capacitor. ;SOLUTION: An overvoltage protective circuit which is a serial combination of a resistor R1 and a varistor VDR, a surge absorbing element, in parallel with a rectifying and smoothing capacitor Ci. When a switch SW is closed and the power is turned on, for example, at a time t0 when a positive period of AC input voltage starts, AC input current during a period t0-t4 which is a first positive period of the AC input voltage becomes excessive rush current due to charging of the smoothing capacitor Ci. However, such conduction voltage as to prevent extreme overshoot voltage is selected for the varistor VDR and therefore overshoot voltage is absorbed by the varistor VDR and the current limiting resistor R1.;COPYRIGHT: (C)1998,JPO