Abstract: A novel topological circuit with full bridge soft switching is developed by adopting phase shift chip UC3879 with current mode and phase shift control.The output waveform characteristics of driving circuit,detecting over current port and main circuit transformer have been researched by practical experiment.Furthermore,based on designing of a large power inverter for arc welding,the soft switching conditions of leading and lagging legs have been analyzed.Following conclusions have been achieved by experiments.No matter what value of the duty is,the primary current of power transformer keeps the maximum value when its primary voltage equals zero.In the midpoint voltage of leading leg transition,its soft switching is easily realized because of the primary current of transformer keeping the maximum.Two pieces of IGBT of lagging leg also achieve soft switching due to the magnetizing inductance participating in the transition of lagging leg.