Patent ID: 8785816

Claim:
A power source for welding; comprising: a first stage to receive a first signal and output a second signal having a first fixed DC voltage; a second stage to receive said second signal and output an isolated third signal having a second fixed DC voltage, said second stage includes an input connected to said first stage; a network of switches coupled to the input and switched at a high frequency with a given duty cycle to convert said input into a first internal AC signal; an isolation transformer with a primary winding driven by said first internal AC signal and a secondary winding for creating a second internal AC signal, and a rectifier coupled to said secondary winding to convert said second internal AC signal into said second fixed DC voltage with a magnitude related to said duty cycle of said switches so as to define said third signal; and a third stage to receive said third signal and output a welding signal, said third stage being separate and distinct of said first stage and said second stage; wherein at least one of said first stage and said third stage is regulated and said second stage is an unregulated inverter stage having a duty cycle of at least 80% and a soft switching circuit without a phase shift modulation, wherein further an energy of said duty cycle being stored in a leakage inductance of said isolation transformer forces a voltage across said network of switches to zero so as to provide an inherent soft switch.