Digital MIG welding power supply system based on bridgeless PFC and LLC

The traditional phase-shifting full-bridge and hard-switching are widely used as a welding power supply (WPS) main circuit topology. However, the phase-shifting full-bridge circuit cannot realize zero-current switching (ZCS) of the secondary side rectifier diode, exhibiting a serious reverse recovery problem. It also has serious secondary duty ratio loss under heavy load and cannot realize zero-voltage switching (ZVS) of the lagging bridge under light load. The hard-switching circuits have some problems, such as low efficiency, switching loss, and serious electromagnetic interference (EMI). The low power factor is another important issue with traditional phase-shifting full-bridge and hard-switching circuits. Given these shortcomings, a digital metal inert gas (MIG) WPS system based on bridgeless power factor correction (PFC) and LLC is proposed, and its principle and application are also investigated. The load simulation and welding process tests of the digital MIG WPS system based on bridgeless PFC and LLC are conducted in this paper. The test results of the simulated load show that the highest efficiency of the PFC is 98.18%, the power factor is 0.999, the highest efficiency of the power supply is 96.3%, and the total harmonic distortion (THD) is 2.0%. The test results of the welding process confirm that the system can achieve full digital control of the welding process, providing a stable welding process and continuously formed weld bead. Moreover, it verifies the feasibility of the digital MIG WPS system based on bridgeless PFC and LLC.