Illinois Tool Works Inc.
METHODS AND APPARATUS TO PROVIDE WELDING POWER

Abstract:

An example welding-type power supply includes: a transformer having a primary winding and first and second secondary windings; an input circuit configured to provide an input voltage to the primary winding of the transformer; first, second, third, and fourth switching elements, and a control circuit configured to: control the first, second, third, and fourth switching elements to selectively output a positive or negative output voltage without a separate rectifier stage by selectively controlling ones of the first, second, third, and fourth switching elements based on a commanded output voltage polarity and an input voltage polarity to the transformer; and prior to changing from a first output voltage polarity to a second output voltage polarity, controlling the first, second, third, and fourth switching elements to reverse the power flow to return reactive energy to an input circuit via the transformer.