PURPOSE: To provide an electric power source device having high reliability at a low cost by correlating the 2nd reference set voltage which determines the max. permissible value of switching current proportonally with the 1st reference set voltage which determines the magnitude of rectified output.
CONSTITUTION: In an electric power source device for welding the 2nd reference set voltage Ef is provided in the 2nd control circuit which turns off the transistors 20, 21 of a switching circui 2, and the circuit is so arranged that said voltage Ef can vary in proportional correlation with the 1st reference set voltage Ed in the 1st control circuit. Then if the voltage Ef is beforehand set slightly higher than the output level of a shunt 80 in the steady time, the output is kept roughly constant even when the magnitude thereof is changed by the voltage Ed. Therefore even when abnormality occurs in the switching current, the semiconductor elements are turned off and the device is protected satisfactorily.
OKUMURA SABUROU
WAKIYA KAZUHISA
ISHII HIDEO
