A zero voltage turn-off high step-up DC/DC converter is presented. The conversion efficiency and power density are improved significantly by using a novel passive snubber cell, which only consists of two diodes and a snubber capacitor. The converter also provides high-voltage conversion ratio as well as low-voltage stress on switches and diodes, which make it suitable for some special industrial applications as electric-vehicle, uninterruptible power supply system or photovoltaic power generation system. The topology, operation principles and performance characteristics are analysed in detail. Moreover, a maximum 800 W experimental prototype has been developed to validate the effectiveness of the theoretical analysis, and 96.2% efficiency has been achieved.