Abstract

This invention provides a small-sized magnetic amplifier with a simple construction. The magnetic amplifier comprises a voltage converting portion composed of a switching element, a transformer and a magnetic amplifier for inducing a pulse signal having a predetermined period and voltage level and converting this pulse signal to a voltage signal, a rectifying and smoothing portion for rectifying and smoothing an output voltage of the voltage converting portion and supplying it for a load, a reset current supplying portion for detecting an output voltage of the rectifying and smoothing portion and comparing it with a predetermined reference voltage, and, when an overvoltage is detected, supplying a reset current to adjust the overvoltage for the output of the voltage converting portion, a reset current limitation portion connected between the voltage converting portion and the rectifying and smoothing portion for forming a discharge loop in which, when a voltage to be outputted from the voltage converting portion has positive value, a flowing current is charged, and when the voltage to be outputted from the voltage converting portion has negative value, the flowing current is discharged, while a discharge path is in direction opposite to a direction of the reset current.