Drive And Protective Circuits Design For Wave Controlled CO₂ Welding Inverter

The drive and protection circuits of inverter welding power source were designed and the main circuit of inverter CO₂ welding power based on arc load was simulated in this paper, it is prepare for developing waveform controlling inverter CO₂ arc welding with high reliability and superiority performance.In gate drive circuit, switch-characteristics were discussed based on working principle and drive characteristics of IGBT. The topological structures of drive circuit of IGBT were designed based on the principle of full-bridge inverter circuit. Then the Matlab simulation proved the rationality of the design. The drive circuit was built with discrete components and satisfied the driving requirement of switching characteristic, to lay foundation for improving the performance of the drive circuit.Over-current protection circuit of IGBT was designed based on the principles of slow decrease of the gate voltage and soft switching over-current protection. When over current occurs, the gate voltage is decreased slowly immediately. The time of supporting the short circuit current is prolonged. At this stage, true and false over-current could be distinguished. And whether protection measures are taken or not could be decided. The parameters about time sequence of protection were calculated based on the type of IGBT module SKM200GB123D. The protection circuit has hold function and can accomplish a whole process of slow decrease of the gate voltage and protection of soft switching. Besides, the influence of the resistance between gate and emitter is analyzed during the over-current protection process. The experiment of this corresponding circuit verified that it satisfied the requirement of time of over-current protection and ensured safe working of IGBT either in over-current conditions.Over-voltage protection circuit is designed based on the principle and parameters of full-bridge inverter circuit. Its working process was analyzed and the effect of RC buffer circuits on turn-off process of IGBT was elaborated firstly. Then the mathematical model in turn-off period of IGBT was founded, which is the important foundation for RC calculation. According to restriction and the specific parameters of main circuit, RC buffer parameters were derived in reasonable switching processes. The over-voltage protection circuit was built based on above works. The circuit can limit the surge voltage under the source voltage in turn-off period of IGBT.In addition, the simulation model of full-bridge waveform controlling inverter CO₂ welding system with IGBT was built by Matlab simulation software. It is the background of analyzing the working of IGBT in the alternative process of short circuit and arc. The output characteristic of IGBT in the type of SKM200GB123D was fitted...