| The lower reliability is the main problem of conventional inverter arc welding power supply which mainly results from hard-switching operation and results in significant switching losses, switching stresses and switching noise. By adopting soft-switching techniques, the switching conditions of power devices can be improved greatly and the reliability of the power supply can be improved accordingly. In addition, the reliability can also be improved by adopting better control mode. In this thesis, the peak current mode is adopted, the model of the welding power supply system is established, and computer simulation is adopted to analyze and design the converter and the system. The range of soft-switching must be rather wide because the load range of arc welding power supply is wide. As for the soft-switching converter in arc welding power supply, the lagging leg is hard to achieve ZVS under low load condition in FB-ZVS-PWM converter. The reason is analyzed and the secondly side auxiliary inductor is proposed to overcome the defect. By computer simulation, the IGBT's turn-off losses which are affected by the parallel capacitor are analyzed. The turn-off losses of IGBT will decrease greatly as the value of parallel capacitor increasing. But the turn-off losses of the lagging leg's IGBTs can not be reduced by this means because lagging leg is hard to achieve ZVS, thus the IGBTs' turn-off losses of lagging leg are remarkable. Fortunately, this defect can be overcome in the FB-ZVZCS-PWM converter, which the freewheeling current can be attenuated to zero and maintained so that the lagging leg can realize ZCS. But in the conventional FB-ZVZCS-PWM converter, the block capacitor is used to attenuate the freewheeling current, which the decreasing rate of freewheeling current depends on the load conditions and the range of ZCS is limited. In this thesis, an auxiliary transformer network is adopted in the primary side of main transformer to attenuate the freewheeling current, which the decreasing rate of freewheeling current do not depend on the load conditions any longer and can be controlled by change the ratio of auxiliary transformer. In this way, ZCS of the lagging lag can be achieved easily under all load conditions. Increasing the value of leading lag parallel capacitor will result in wide variational range of the leading lag's shifting time, which contradicts that the dead time of leading leg is constant in the conventional phase-shifted control mode. However it can be overcome by adopting limited bipolar control mode, which is more fit for FB-ZVS-PWM or FB-ZVZCS-PWM converter in the arc welding power supply. In conventional inverter arc welding power supply, voltage mode is mostly adopted, which contains only one control loop. In this mode, the transient response is slow, and it can't provide the flux balancing of the main transformer and current limited of power devices, which decreases the reliability of the power supply. In this thesis, peak current mode is adopted in control circuit, which contains two loops. It's inner loop controls the peak current of IGBTs in each period, therefore the flux balancing is obtained automatically and the transient response is improved greatly, while it's outer loop controls the output average current of power supply. In order analyze and design the power supply system, the system models which control by two above-mentioned control modes are established and analyzed by computer. The analysis results show that in peak current mode, the output inductor is "absorbed" in the inner loop, the control to output character is a proportion character within half of converter operation frequency and it's independent of the load conditions. The compensation network is easy to design and the system performance is obviously better than that in voltage mode. Based on the above-mentioned results, a welding machine is developed, which can be used for MMAW (manual metal arc welding) and TIG welding. The control circuit of out characteristics is designed according to the characteristics of welding processes and the output current ranges from 20A to 400A.
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