Soft switched flyback DC-DC converter for wide input voltage and full load range applications

Soft switching techniques have a very important role in reducing the size, cost and also in improving average efficiency and power density of dc-dc converter. This paper introduces a soft switched flyback dc-dc converter with zero-voltage switching during both turn on and off. The soft switching is obtained over wide load and line ranges by placing two small ac capacitors in both side of flyback transformer. The triggering for switches is given by measuring the magnetizing voltage and current. This method provides zero-voltage switching during turn on and turns off independent of line voltage and load resistance. The new converter has four modes of operation which is described in this paper. The overall size of the system is reduced by increasing the switching frequency. In order to provide constant output voltage, current reference control is employed. The simulation results under different load and line conditions are provided to verify the performance of the new converter.