Digital Control for an Arc Welding Machine Based on Resonant Converters and Synchronous Rectification

This paper presents a field-programmable gate array (FPGA)-based generation of optimized drive signals for resonant converters using synchronous rectification (SR) applied to an arc welding machine. The proposed digital implementation makes the most of the FPGAs capabilities by setting in open loop the arc welding current with enough resolution to establish precisely the operation point, according to the welding technique and metal part requirements. It also optimizes other parameters of interest such as the initial and final welding transient. The resulting system is very flexible because is valid for Tungsten inert gas, shielded metal arc welding, and metal inert gas welding techniques. A novel ad-hoc SR control algorithm for current mode operation that eliminates the dead-times of the power MOSFETs´ switching period is proposed. Finally, the experimental results are presented including an efficiency comparison between diodes and SR solutions.