A teardown of a Migatronic FocusStick 161E stick welder. I take apart and show the current paths of the system. This stick welder is adjustable from 20 to 160 Ampere.
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The unit is built around a single printed circuit board that hosts both the input filter, rectifier, PFC frontend, high voltage igniter and high current inverters, as well as the output transformer. Only the PFC choke is external to the PCB.
The heat sinks are live with one leg of the half bridge inverters. The forced air cooling tunnel also doubles as a space filler between the isolated heat sinks. There is a few different interesting parts found in the welding inverter. There is the diodes SSTH30R06W (600 V / 30 A) and F60UP30DN (300 V / 30 A). There is also FGH60N60 (600 V / 60 A) IGBT.
The controller board has a single Texas Instruments UC3846 IC. This chip is a dual ended 500 kHz current mode PWM controller. There is a few other controller ICs hidden in the white formal coating / anti-vibration glue on the PCB.
