PURPOSE: To suppress abrupt variation of common mode voltage upon recovery of power by providing means for short-circuiting a current limit element upon elapse of a predetermined time after detection of recovery of AC input through an AC input voltage detecting means.
CONSTITUTION: During power interruption when a switch 2 is opened, a relay 15 does not function and the contacts thereof are opened. Upon recovery of AC input, the relay 15 functions to close the contacts with a predetermined time lag. A capacitor 12 is discharged through a resistor 16 immediately upon recovery of power, and common mode output voltage varies slowly. The contacts of the relay 15 close upon elapse of the predetermined time and discharge of the capacitor 12 has been substantially completed at that time point. Consequently, abrupt variation of common mode voltage can be suppressed upon recovery of power.
UEDA KIYOSHI
WATANABE TSUTOMU
TADA YUKIO
