Abstract: A novel topology of half-bridge circuit, which is used as the secondary inverter of a variable polarity welding power supply, is proposed, and it is composed of a coupling inductor, a half-bridge circuit realized by two IGBTs and their RC snubber circuits.This kind of secondary inverting circuit could provide a high commutation rate of welding current from one polarity to another during the process of polarity exchange, and it could also generate a high enough voltage to re-ignite the arc when current zero-crossing.The control strategies of switches exchange and exchange current are also researched for the better and reliable control of the welding power supply system.Experimental results show that the welding power supply system developed here has an excellent polarity exchange performance and the advantages of simple structure, low cost and high efficiency, and thus has broad prospects of production application.