Patent ID: RE39926

Claim:
An arc-machining power supply comprising: a DC circuit that outputs DC voltage; an inverter circuit that includes a pair of first and fourth switching elements and another pair of second and third switching elements, the first to the fourth switching elements being connected to form a bridge circuit for converting the DC voltage to high-frequency AC voltage; a transformer that converts the high-frequency AC voltage to a voltage suitable for a desired arc-machining process; a rectifier circuit that rectifies the voltage converted by the transformer for output of DC voltage; a power on/off device arranged between the DC circuit and the inverter circuit for controlling an output from the DC circuit to the inverter circuit; an auxiliary capacitor for turning on the power on/off device when input voltage to the power on/off device is substantially equal to output voltage from the power on/off device; an output control circuit that supplies first and second output control signals for performing required feedback control, the first output control signal being offset from the second output control signal by half a cycle; a power on/off driver that turns on the power on/off device when the first output control signal changes to a high level, and turns off the power on/off device when the first output control signal changes to a low level; and an inverter driver that turns on the first and the fourth switching elements when the first output control signal changes to the high level, and turns off the first and the fourth switching elements when the first output control signal changes to the low level and a predetermined capacitor discharge period elapses, the inverter driver being also arranged to turn on the second and the third switching elements when the second output control signal changes to a high level, and turn off the second and the third switching elements when the second output control signal changes to a low level and a predetermined capacitor discharge period elapses.