Abstract: An improved phase-shift full-bridge zero-voltage zero-current switching (ZVZCS) welding inverter is proposed. By DC block capacitor in series with primary of the transformer, and a saturable inductor in series with the lagging-leg switch, the zero-voltage turn-on for the leading-leg could be achieved due to the energy stored in the output inductor and the leakage inductor, the zero-current turn-off for the lagging-leg could be achieved due to the resonant between the DC block capacitor and the leakage inductor, and the reverse current was blocked by the saturable inductor. Thus, the excessive core losses of the saturable inductor in the conventional ZVZCS converter could be overcome, since the inductor was unidirectional saturable. It was especially suitable for high power applications. The principles of operations and the soft-switching operation range were discussed simply. Finally a 3 kW welding inverter was implemented, and the experimental results were also presented to confirm the validity of the proposed inverter.