RECTIFYING AND SMOOTHING CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide a rectifying and smoothing circuit which can set a DC voltage to be output to a predetermined specific voltage VSor lower even when the maximum voltage value of the AC voltage to be input is abnormal, and which can output stably the DC voltage even when the maximum voltage value is the specific voltage VSor lower. SOLUTION: The rectifying and smoothing circuit includes a control circuit (21) for controlling to open or close the first switch element (11) connected in series with a first rectifying circuit, and a second switch element (12) connected in series with a second rectifying circuit; and a comparator (21) for comparing a voltage across a capacitor (7) with a predetermined specific voltage. When the voltage across the capacitor (7) exceeding the specific voltage is detected by the comparator (21), the first switch element (11) or the second switch element (12) controlled to be closed is controlled to be opened, and the first rectifying circuit or the second rectifying circuit is cut off. When a charging voltage exceeds the specific voltage VS, the current flowing to the first rectifying circuit or the second rectifying circuit flowing the charging current to the capacitor (7) is cut off, and hence the charging voltage (output voltage) of the capacitor (7) is controlled to the specific voltage VSor lower. COPYRIGHT: (C)2004,JPO