In a
welding power supply for creating
welding current in a succession of current pulses with a maximum current level and a trailing off state which current pulses passing through a series circuit including an
inductor and
electrode in
welding relationship with a workpiece wherein the power supply has (a) an
inverter stage with an input to be connected to a power source, a first terminal at a first
electrical polarity when the
inverter is on, a second terminal at a second
electrical polarity when the
inverter is on, and a control to generate an off
signal to turn the inverter off and remove current from the terminals to shift said
current pulse toward an off state; and, (b) a
power switching stage including a
transistor based switch having a conduction condition passing current from the first terminal upon creation of a first logic
signal and a non-conduction condition blocking current upon creation of a second logic
signal, the improvement comprising: a sensor for measuring the instantaneous value of the welding current, a
comparator for producing a low current signal when the instantaneous current is at a selected value substantially below the maximum current level and a circuit or program for creating the second logic signal upon production of a low current signal after generation of an off signal whereby the
transistor based switch is switched from the conduction condition to the non-conduction condition when the welding current is generally at the selected value.