Abstract: A power source for an arc welder which employs a high voltage, short duration impulse for periodically exciting an arc for use in arc welding. The device operates from an AC power source and employs a single silicon controlled rectifier (SCR) which is triggered in response to the output of a voltage controlled oscillator. The frequency of the voltage controlled oscillator is controlled by a programmer in conjunction with a feedback signal which is in accordance with the arc welding current, the output of the voltage controlled oscillator thus being varied as needed to maintain the welding current at the value programmed by the programmer. The output of the oscillator is divided down to produce a series of pulses which are used not only to trigger the SCR but also to trigger the arc starter and provide synchronization for the programmer. An inductor is used to commutate the SCR, i.e., cut the SCR off a predetermined time period after the triggering thereof.