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Non-isolated high step-up DC-DC converters are required widely in the industrial applications. Many of these conventional DC-DC converters have the disadvantages of operating at high duty-cycle, high switch voltage stress and high diode peak current. The proposed converter can provide very high voltage gain without operating at high duty-cycle by employing a coupled inductor, a switched capacitor and an additional diode. At the same time, the switch voltage stress is reduced greatly, which is helpful to reduce the conduction losses by using a low on-resistance switch. The presented converter employs a passive lossless clamp circuit instead of an active clamp circuit to recycle the leakage energy, which is simpler and easier to design. Zero-current switching turn on performance is achieved due to the leakage inductance, and the switch voltage is clamped to the voltage on the clamp capacitor, which is helpful to reduce the switch voltage stress. Moreover, the reverse-recovery energy of the output diode and the leakage inductance energy are recycled. Finally, a 500-W prototype has been built to verify the analysis. The maximum efficiency of the prototype is 96.9% and the efficiency is higher than 96% over a wide load range.