Research On AC/DC Square Wave Inverter Welding Power Source Based On DSP Control

The appearance and development of digital inverter welding power source are the improvement of welding technology. It is said that digital inverter welding power source is the digital revolution or IT revolution of welding technology. It not only promotes development of welding power source, but also takes good acts on the future developents. This paper introdues the cencept of digitalization firstly, then analyzes the characteristics of digital inverter welding power source. According to the research trend at homeland and overseas, it is very necessary to research.The application field and development trend of DSP are introduced briefly and its work principle, stucture characteristics and select are explained in detail. This paper emphasizes on the component parts and control principle of digitalized IGBT inverter AC/DC square wave welding power source. Main circuit, control circuit, protection circuit and drive circuit are respectively analyzed. Otherwise, the software and hardware are also interpreted.Main circuit, which applies IGBT full-bridge inverter structure, is made up of rectifier, filter, high-frequency transformer and the latter inverter. The key points and the parameters of design are discussed detailedly. High performance 16-bit DSP TMS320F240 is adopted as control kernel. Using universal PWM method means to control output power and output characteristic through controlling IGBT switch on time. Because TMS320F240 can not directly generate requisite pulse waveform with dead-band, a special separate frequency circuit is designed. The former separate two pulses trigger IGBT after they are magnified by exclusive drive module M57959L. The latter separate two pulses trigger IGBT after they are magnified by special circuit. The system samples output current in real time and bring it to DSP for A/D conversion.This paper also intruduces the resource distribution and the function of outer circuits.Aim to typical problems in welding process: over current, over heat, over voltage and lack voltage, a corresponding protection circuit is designed. The stucture and function of main program and interrupt service subroutine are explained.The installation and setup of DSP develop environment CCS and develop tool XDS 510 are illuminated, too.Corresponding data and waveforms are recorded in the experiment, and problems occurred in experiment are investigated. The experiment results show that the inverter power source has rapid response-speed, high reliability, a strong ability ofanti-jamming.At last, some advices on future research for the welding power are given, and they will make a found ground for tomorrow's research of digital welding power.