This paper proposes the use of a control algorithm that can yield soft switching both at turn-on and turn-off of the inverter of series resonance converter (SRC) gas metal arc welding (GMAW) machines. The technique takes advantage of the band-pass filter characteristics of the SRC and controls the power by using switching frequencies that are subharmonics of the resonance frequency. The design and the experimental results for a 5 kW prototype system are given to prove that the algorithm can be used in GMAW systems.