Stabilized welding power source including a series-resonant

Abstract

A pulse arc welding power supply incorporating one or more series resonant converters (SRC) for converting D.C. power to A.C. power which is then rectified to supply welding current. Each series resonant converter includes a series resonant tank circuit consisting of a capacitor, an inductor and the primary winding of a transformer whose secondary winding supplies current to the welding arc. The undesirable secondary output capacitor of the prior art is eliminated, as all the capacitance in the series resonant circuit is located on the primary side of the transformer. Current sensors sense the ringing current in the resonant circuit and also the load current and produce respective feedback signals which are used to control the switching frequency of an SCR bridge in the tank circuit, thereby maintaining the welding current at a desired value. Inner and outer current regulating loops, including a ramp generator, compensate for non-linearity in the continuous conduction mode of the SRC by limiting the switching frequency of the SCRs. a fault-predicting circuit also further limits the switching frequency in the continuous current mode for additional protection.