| Electric welding, considered as the sartorius of industry, played an indispensable role. Its core, DC converter arc welding power supply had some special advantages, such as dynamic response quicker, control degree accurater, which made it applied more widely. But there were several limitations in the terms of the efficiency, EMI and reliability for the whole machine.The output power of inverter arc welding power supply was a litte bit bigger, whose load worked in the following rules "idle load -short circuit-drawing arc-burning arc-short circuit-drawing arc". So its radiation and conductive interference were more serious. Old fashion auxiliary power supplies included several independent linear power supplies, which offered power to control circuit, testing circuit and drive circuit separately. Each drive circuit must have its own linear power supply to avoid the interference between the drive signals. Once the output of linear power supply was short, the power supply can't protect itself. The converter DC arc welding power supply was easy to be mangled because of abominable working situation.And the linear power supply bigger and its efficiency was lower.Compared with integrated auxiliary switch power supply with multi-output, its cost was bigger. So a novel auxiliary power supply of inverter arc welding power supply control system, which was safer, more credible, more economical and more practical, was developed.After researching the characteristics of almost all kinds of adoptable circuit topologies, one practical auxiliary power supply of DC inverter arc welding power supply control system was designed. It adopted two-transistor flyback converter as its main circuit, which was suitable for multi-output and higher voltage input. TL3844, which worked in the peak current control method, was used to constitute the control system. The power supply solved the problem that there must be some independent linear power supplies to offer power for all parts of control circuit.The working principle of the auxiliary power system was analyzed in detail and some rules and method for the design of the central parameters were given. And how the auxiliary power supply was used in the DC inverter arc welding power supply controlsystem was introduced and some parts were also presented.The research was helped by dint of Computer Aided Design (CAD) technology. The DC and AC small signal models, working in different mode, were set by the means of state space average method, and the transfer functions were concluded accordingly. And their bode diagrams were gotten from MATLAB. Some appropriate compensation networks and feedback system were designed. The dynamic character, stability and anti-interference were analyzed. The mathematics model of feedback circuit was derived from the actual control system and the simulation waveform of output voltage was given. The optimization of system parameters was processed.A switching power supply, with input voltage three-phase, 380V/50Hz, AC, and eight isolated outputs, was designed and built. The experimental and simulation results proved that the topology of two-transistor flyback converter not only kept the excellence of single-end flyback converter, such as easy construct and multi-output, but also improved its security and dependability in high-voltage situation. The auxiliary power supply was able to satisfy the demand of digital DC converter arc welding power supply and take the linear power supply's place. |
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