Research On Chopper Control Of TIG Welding Power Source

The DC TIG have good stable welding parameters, good observational arc, and it is easyto obtain stable welding quality. It is widely used for welding important structures. DC pulseTIG adopt pulse current, and it can get larger penetration and low heat input under theconditions of lower average welding current. Pulse frequency can be increased to improve thearc pressure and the quality of welding.This paper studies the DC pulse TIG high frequency pulse control technology. Applypower MOSFET device as a switching device, and adopt DC chopper control technology toresearch and design high frequency DC pulse TIG welding power system. This systemincludes power chopper system, frequency pulse-width adjustable digital control systems,drive systems and so on. Power chopper system adopt power MOSFET device, its model isIRF450. Frequency pulse-width adjustable digital control system is composed of4M clocksource, decimal counter system, trigger and conversion counting system, start control circuit,counting adjustment portion and so on. Drive system is composed of photoelectric isolationdevices, level shifting circuit, power driver circuit and so on.The frequency of adjustable frequency pulse width digital control system can be controlfrom9.523Hzto109.89kHz, in the condition of4MHz clock source without frequencyreduction. Through adjusting the pulse width, the duty ratio can be adjusted from1%to99%.It can meet the frequency and pulse width of pulse welding requirements. Due to the highspeed photoelectric isolation devices, the output drive voltage switch fast between+12V and-5V, and the conversion process of its rise and fall is very fast. It can meet the requirement ofthe chopper control TIG high frequency pulse current. Power MOSFET is connected inparallel by many single tubes, the chopper control to meet the power requirements. Theswitching frequency of power MOSFET chopper control device can get100kHz or more, andit can meet the design requirement.After manufacturing, testing and welding experiment of the high-frequency choppercontrol TIG power systems, the pulse frequency of pulse welding current reached11.364kHz.Using this system to weld0.3mm stainless steel sheet, and the welding process is stable, theweld is beauty. Experimental results show that the designed chopper control TIG power system structure is reasonable and the system is stable.