Wide range ZVS active-clamped L-L type current-fed DC-DC converter for fuel cells to utility interface: Analysis, design and experimental results

A wide range zero-voltage switching (ZVS) active-clamped L-L type current-fed isolated DC-DC converter is proposed for fuel cells to utility interface application. The proposed converter maintains ZVS of all switches from full-load down to very light load condition for wide input voltage variation. Detailed operation, analysis, design, simulation and experimental results for the proposed converter are presented. The auxiliary active clamping circuit absorbs the turn-off voltage spike and also assists in achieving ZVS of main switches. The ZVS of auxiliary and main switches is achieved by the energy stored in the boost inductors and series inductor (aided by parallel inductor), respectively. Rectifier diodes operate with zero-current switching. An experimental converter rated at 200 W has been designed, built and tested in the laboratory to verify the analysis, design and performance of the proposed converter for wide variations in input voltage and load.