Second Stage Half Bridge Inverter Design in AC TIG Welding Machines

In AC tungsten inert gas (TIG) welding machine application, there are two kinds of commonly used topologies of the second stage half bridge inverter circuit. This paper analyses and compares these two topologies. In addition, in the second topology, more investigations have been made to show the factors that can affect the changing rate of the output current as well as the factors that can affect the current transformation ratio in the coupled inductor. High changing rate and high current transformation ratio are the two important requirements of the electrical power source for AC TIG welding, however, in the conclusion of the analysis, it is difficult to meet these requirement at the same time. Therefore, a solution by adding extra voltage sources across the rectification circuit is proposed to maintain the high changing rate of the output current as 7A/µs and achieve about 100% current transfer in the coupled inductor.