Modular power source for electric ARC welding and output chopper

A power source for an electric arc welding process, said power source comprising:

• a first module including:
• an input stage having an AC input and a first DC output signal;
• a second stage in the form of an unregulated DC to DC converter, unregulated by a feedback signal from the electric arc welding process, having an input configured to receive said first DC output signal, a controller configured to operate a network of switches at a frequency greater than 18 kHz with a duty cycle to convert said received first DC output signal 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 to convert said second internal AC signal into a second DC output signal of said second stage, said second stage having a fixed relationship between input and output voltages of the second stage;
• and
• a second module including a third stage to convert said second DC output signal to a welding output for welding in said process, said input stage and said second stage being assembled into said first module and said third stage being assembled into said second module so as to be releasably connectable to said first module.