| The application of inverter technology in welding power makes rapid development of welding equipment getting smaller and higher frequency. However, the shortcomings of traditional analogue circuit control have become the bottleneck for further promotion of the welding inverter power. This paper introduced the digital concept of welding power and analyses advantage and disadvantage of MCU, MPU, and DSP. according to current research status in domestic and overseas and the characteristics of digital signal processing, this paper illuminated necessity for this article.DSP' s development history is briefly introduced and the inner structure, working principle and program control measure of DSP—TMS320F240 is also detailed explained. Furthermore, reason for select this type DSP as controller is given. After made sure controller, the paper given design thoughtfulness, project and aim for the welding power.Main circuit, which applies IGBT full-bridge inverter structure, is made up of rectifier, filter, high-frequency transformer and output reactance. The key points and parameters of the design are discussed in detail. Even current and pulse current were also illuminated.High performance 16-bit DSP TMS320F240 is adopted as control kernel. Under the action of main modules: DSP minimize system, parameters presetting and display module, voltage and current real time sampling module and protect module, real time close loop control and real time protect of the welding power is applied. Using universal PWM method means to control output power and output characteristic through controlling IGBT switch on time. Because TMS320F240 can not directly generate pulse waveform with 180° phase error, a special separate frequency circuit is designed. It can separate two pulses to trigger IGBT after they are magnified by exclusive drive module M57959L. The system real time sample output current and welding voltage, and use PI control algorithm realize the purpose of control output characteristics of welding power.Parameters presetting and display module circuit in the design apply two digital pant meter s as main display instrument. When parameters are presetting, digital pant meters display presetting parameters. When the power is welding, digital pant meters display welding process parameters: voltage and current. A separate switch circuit was designed to switch the two kind of display. Furthermore, algorithm in program was also workout to make the value displayed the same as the value in DSP.Aim to typcal faults in welding process: over current, over heat over voltage and lack of voltage, a corresponding protect circuit was designed. Switching wire-feed circuit was also designed in the control system.Reliability and anti-jamming are considered in main circuit and controlcircuit. System software, which is made of modular subroutines such as main program, interrupt service subroutine and so on, are very efficient for limiting noise and improving system response-speed.The circumstance of emulation is necessary for developing DSP system. The paper illuminates DSP develop circumstance CC 'C2000 and develop tool XDS 510 in detail.Corresponding data and waveforms are recorded in experiment, and problems occurred in experiment are investigated. The experiment results showed that the inverter power source has rapid response-speed, high reliability, a strong ability of anti-jamming and good human-computer interface.At last, some advices on future research of the welding power are given, and they will make a found ground for tomorrow' s research of digital welding power. |
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