A passive lossless snubber cell with minimum stress and wide soft-switching range

A passive lossless snubber cell and its dual structure for reducing the switching loss of a range of switching converters are presented. The proposed snubber cell has several advantages over existing snubbering techniques. First, it provides zero-current-switching (ZCS) and zero-voltage-switching (ZVS) conditions for turning on and off, respectively, the switch over a wide load range. Second, it does not introduce extra voltage stress on the switch. Third, by taking the ripple current through the switch into account, the peak switch current during the snubber resonance period is designed to be less than the designed switch current without the snubber. Hence, the proposed snubber does not introduce extra current stress on the switch. The operating principle, procedure of designing the values of the components and soft-switching range of the snubber will be given. Connections of the snubber cells to different switching converters will be depicted. A performance comparison among the proposed snubber and two previously studied snubber cells will be addressed. The proposed snubber has been successfully applied to an example of a 200W, 380V/24V, 100kHz two-switch flyback converter operating in continuous conduction modes. Experimental results are in good agreement with the theoretical predictions.