| A soft-switching converter circuit is discussed on the basis of analysis of the hard-switching power converter circuit's shortcoming in the paper. The definition, classification, development and the control strategy of the soft-switching have been summarized. The principle of operation, features of the general pulse-width modulated (PWM) power converter of zero-voltage-switching(ZVS) with phase-shift control are described.Its merits and shortcoming are pointed and some measures used to improve the circuit performance are given. Then a novel zero-voltage-zero-current full-bridge PWM soft-switching power converter is proposed. The new converter overcomes the limitations of the ZVS-FB-PWM converter ,such as the high circulating energy ,bad loss of the duty cycle, and limited the ZVS load range for the lagging-leg switches. By using the dc blocking capacitor and adding a saturable inductor and adding two diodes in the main channel., the primary current during the freewheeling period is reduced to zero. And allowing the lagging-leg switches to be operated with zero- current-switching ,meanwhile, the leading-leg switches are still operated with ZVS .The circuit topolQgy , principle of operation ,circuit features have been described detailedly. Based on the new circuit topology, an experiment of high-voltage,high-power DC-DC converter is presented where IGBTs are predominantly used as the lagging- leg switches. The design of structure and calculation methods of parameter in the DC- DC converter main circuit and the design of the control and protect circuit have been presented. The phase-shift control is implemented with UC3 879. The experiment results show the circuit topology is right. |
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