A New High Step-Down Converter with Lossless Passive Snubber

In this paper, a new non-isolated soft switched DC-DC converter with high step-down conversion ratio is proposed. The proposed converter consists of two switch cells that their inputs and outputs are cascaded. This converter provides ultra-high step-down conversion ratio and due to all semiconductor devices are soft switched, switching losses are reduced, also reverse recovery losses of diodes are reduced because of ZCS turn off condition. The duty cycle of proposed converter is much larger than step-down converter and therefore does not have the problems of the converter with a narrow duty cycle and since no auxiliary switch is used to achieve soft switching, the control circuit remains simple. In this paper, the convertor operating modes are discussed and to verify the performance of the converter a 50W prototype with 100 kHz switching frequency, 100V input and 16V output is built. The converter efficiency is measured and the peak efficiency is 94% also the conducted electromagnetic interference peak in the proposed converter is reduced by 6dBµv.