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For step-up applications,a conventional boost dc-dc converter is normally adopted.However,its voltage gain is not enough for high-step-up applications.To obtain high-voltage gain,many solutions have been studied.As the simplest methods,the boost converter can be cascaded or stacked up on the other step-up converter.However,the cascade structure requires a lot of components as numerous as the count of the stages,which brings on low efficiency,complex circuit,and high cost.Therefore,it is commonly integrated as a single-switch converter by sharing the main switch in order to reduce component count and circuit complexity.However,the conduction loss and switching loss is increased because each stage of the inductor current flows in one common switch.Hence,the sort switching is needed to improve the power efficiency.There are several high-step-up stacked boost converters.The stacked-up structure is generally that both dc-dc converters are connected up in parallel by the coupled inductor to obtain high-voltage gain.Since the output capacitor is connected in series,the voltage balance of the output capacitors should be considered.But there efficiency is not much high and also have some disadvantage so a new approach has been done in this thesis to overcome previous problems.This thesis focuses on the new approach to develop an efficient Boost Converter by using coupled inductors.In order to eliminate voltage spikes,a buffer circuit is used in the converter.Coupling coils generate leakage flux,and energy in the leakage flux causes voltage spikes.With a high boost ratio,the active switches in the converter can maintain the proper duty cycle,which can significantly reduce voltage and current stress.Since the main switch and the auxiliary switch can be tumed on by the zero voltage switching,the switching loss is reduced,and the conversion efficiency is significantly improved.In this paper,an experiment was conducted by building a200W boost converter model.The results show that the conversion efficiency is greater than90％,and the surge phenomenon can be effectively suppressed.Finally,the feasibility of low-voltage input systems was verified by photovoltaic and battery system.