Since the advent of high-power semiconductors such as the IGBT, it is now possible to build a switching power supply capable of coping with the high loads of arc welding. These are known as inverter welding units. These supplies generally convert utility power to high voltage and store this energy in a capacitor bank; a microprocessor controller then switches this energy into a second transformer as needed to produce the desired welding current. The switching frequency is very high - typically 10,000 Hz or higher. The high frequency inverter-based welding machines can be more efficient and have better control than non-inverter welding machines.

The IGBTs in an inverter based machine are controlled by a microcontroller, so the electrical characteristics of the welding power can be changed by software in real time updates. Typically the controller software will implement features such as pulsing the welding current, variable ratios and current densities through a welding cycle, variable frequencies, and automatic spot-welding; all of which would be prohibitively expensive in a transformer-based machine but require only program space in software-controlled inverter machine