Research Of Transistor Type Resistance Spot Welding Power Supply With Waveform Control

Resistance Spot Welding (RSW) is widely used in welding electronic devices, medicaldevices and sensors, etc. The sizes of these products are so tiny, which makes weldments hardfused and influences the welding quality. The three main factors that influence the quality ofthe resistance spot welding are welding current, electrode pressure and welding time. Thepaper is based on the effect of welding current and welding time, designing a transistor-typeresistance spot welding power supply, which controlled by the core of DSP. The design canmeet the needs of the precision welding, through improving the control precision andresponse rate of the welding current and welding time.This paper determines the main circuit, which is based on the chopper technology oftransistor, through discussing the design schemes of power supply. The feature of the designdoesn’t contain welding transformer and output rectifier module. The main circuit consists ofcharging circuit and welding circuit. In charging circuit, the capacitors are charged with theconstant current, which can achieve a rapid, stable and controlled charging process. Inwelding circuit, the outputs current is controlled by the MOSFETs chopped circuit. This paperuses reasonable measures to parallel MOSFETs, which solves the capacity shortage ofindividual MOSFET and the problem of current sharing, and improves the output power.Besides, the paper designs the hardware and software of the control system based ondsPIC33FJ64GS610, which improves the control precision and response rate of power supply.Finally, the paper build the experiment platform of power supply and complete thedebugging. The result demonstrates that the design can achieve the constant current chargingfor capacitor group, improve the efficiency and stability in the charging process, and achieverapid and precise control of the welding current output through transistor chopper circuit.Compared with the other common resistance spot welding power supplies, it proves that thetransistor resistance spot welding power supply has the advantages of rapid current controlresponse rate, stable output current, high time adjusting resolution and controllable currentwaveform.