Many applications, such as photovoltaic systems, uninterruptible power supplies, and automobile headlamps, need high step-up DC-DC converter without isolation. Conventional boost converter has the advantages of simple topology and easy control. However, it has some shortcomings, such as insufficient step-up voltage ratio and poor efficiency when operating at large duty-cycle conditions. One of the popular topologies used is the coupled inductor boost converter to overcome these problems. It utilizes the turn ratio of coupled inductor to realize the higher step-up voltage ratio. However, the leakage inductance of coupled inductor causes huge voltage spike when the power switches are turned off. Moreover, the large root-mean-square (RMS) current flows through the primary side of coupled inductor due to the low input voltage conditions, thereby resulting in a large copper loss. This paper proposes a novel high step-up boost converter with dual coupled inductors to solve these problems. This proposed converter employs dual coupled inductors, and the input side shares RMS current into two separated primary sides of the coupled inductor. The secondary side of coupled inductor is connected in series to increase the step-up voltage ratio. The proposed converter utilizes active clamping to achieve zero voltage switching (ZVS) for suppressing voltage spike and improving conversion efficiency. The proposed converter and its control method are introduced. The operation principle, circuit characteristics, and circuit analysis are presented. A prototype converter with 300 W output power 25–40 VDC input voltage and 200 VDC output voltage is implemented. All functions, including high step-up voltage ratio, ZVS, and active clamping, are achieved, and the highest efficiency is around at 94.7%.
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