Research Of Soft Switch CO₂Welding Machine Based On DSP TMS320F2812

In recent years, welding technology,one of China’s important industrial productiontechnology, has been rapidly developed welding process,and the requirement of welders andother supporting equipment is also rising. With the popularity and massive production ofwelders the performance of welding power source, the main components of welders, havebeen greatly concerned by users and producers. Through analyzing the classification,characteristics, application and development trend of welding power source home andabroad,it points out the necessity of the transition from analog to digital and the role of softswitch in welding power, which made the purpose and significance of this research.The paper analyzed and studied the concept and characteristics of digital weldingpower source and the main types a soft switching circuit. Determined to use thephase-shifted full-bridge zero-voltage and zero-current (Zero Voltage Zero Current----ZVZCS) as the main topology. Firstly,elaborated the commutation process of ZVZCS softswitching circuit on each period, indicated that the tubes on forearm may achievezero-voltage switching on and off, while lagging arm is at the zero current turn-on andturn-off state. Secondly, calculated the parameters of some important electronic componentsin the circuit to determine their types, including: IGBT, forearm switch on ultra-capacitorsand blocking capacitor in parallel resonant inductor and the secondary rectifier diode. Afterdetermining the parameters of the electronic components, use software Orcad PSpice tomake a simulation of ZVZCS circuit, and then output and analyze the simulationwaveforms.In this paper, design of the hardware of is based on TI DSP chip of TMS320F2812models. The design of hardware includes: a signal acquisition circuit for welding parameters,i.e.use the Hall sensor to collect the welding current/voltage signal which will be sent tothe DSP, and an AD converter module change them into digital signal which is available toDSP; IGBT driving circuit,constructed by an drive plate whose core piece is KA962F,amplify the power of the PWM output by DSP, to drive the IGBT on and off; power supplycircuit section comprises three parts: DSP power, IGBT driver board power supply and wirefeeder drive; the design of DSP and PC communication circuit is mainly based onMAX3221E chip, realizing the communication of DSP and PC via RS232serial port;protection circuits includes three parts which are over/under voltage, over current and overheat protection circuit; smart start control circuit of welders, is developed around themain function of MFRC500RF chip.In this paper, the design of software portion is based on a concept of modular design,from whole to part, through the DSP compiler software CCS3.3, making comparison andchoice of control algorithm, output PWM waveforms with dead band; achievehuman-computer interaction design based on MCGS software.Finally, with the integrated design of hardware and software, completed the studies ofsoft-switching CO2welding machine control system on DSP, and made some experimentsand testing on the system, the results of the design is that the system showed a stableperformance, and the design achieved the desired requirements.