A two-stage power converter for welding applications with increased efficiency and reduced filtering

The power supply technology used in welding applications changed dramatically from manually tap-controlled 50 Hz bulky transformers which had large leakage inductance to provide stable arc burn to switch-mode fast controlled high-frequency power electronics. Nowadays, the typical converter configuration consist of a diode rectifier supplying via a large electrolytic capacitor a smooth DC-link voltage to a high switching frequency H-bridge inverter that steps down the voltage and provides isolation via a high frequency transformer whilst operating with adjustable duty-cycle to maintain the output current constant. This topology allows for important size reduction since the size of magnetics decreases rapidly with the increase of the frequency. This paper proposes a more complex two-stage configuration with a buck DC/DC converter operating at a reduced switching frequency to feed adjustable voltage to an H-bridge inverter, which is operating always with the required voltage at 50% duty-cycle, enabling in addition the minimization of the output filter size and of the switching losses.