In this application note, a power AC-DC converter suitable for use as the current supply for the MMA welding process is described. The MMA welding method is the most common method used for welding iron or steel. In recent years, the availability of low-cost and reliable solutions based on power electronics has shifted the approach to this application from a standard magnetic solution based on a low-frequency iron transformer to a high-frequency switching solution. This allows for compact and lightweight solutions at a relatively low price. The electronic control used in modern welding machines enables simple and safe use, so even an unskilled person can achieve good weld quality.