Abstract: In order to reduce the switching loss and ripple of output voltage of CO₂ inverter welding machine and realize the digital control,the soft-switching commutation principle of halfbridge DC-DC converter with adding two assistant power switches to DC busline side is analyzed in this paper.Based on ARMcontrolled and double closed-loop(current and voltage) control strategy,a full digital CO₂ inverter welding machine is designed.The soft-switching commutation of new half-bridge DC-DC converter is simulated in the Matlab/Simulink environment.The experimental results illustrate that the full digital ARM-controlled new half-bridge soft-switching inverter welding machine has significant advantages over the traditional analog-controlled inverter welding machine,such as low switching loss,low voltage ripple,flexible programming ability and better stability.