Z-source converter has several advantages such as high-voltage gain, clamped switch voltage and positive output voltage polarity. This study presents a new non-isolated high step-up DC-DC converter which is derived from Z-source converter and provides higher-voltage gain compared with its conventional counterpart. Owing to its highvoltage conversion ratio, the proposed converter is a proper choice for photovoltaic applications. Furthermore, reverserecovery problems caused by the output diode are reduced in the proposed converter which reduces the switching losses. In addition, the leakage energy is recycled so the conversion efficiency is improved. Analysis and operating principles of the proposed converter are discussed and design guidelines are presented. Moreover, the effect of nonideal elements on the proposed converter performance is analysed. A 100 W laboratory prototype to convert 20-300 V is implemented and experimental results are presented to verify theoretical analysis.

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This study presents a four-phase interleaved buck converter with low voltage stress and high step-down conversion ratio. The proposed converter provides an extended duty cycle and low voltage stress for switches and diodes, in high step-down applications. This makes it possible to use switches with lower voltage rating and thus reduce both switching and conduction losses to improve the overall efficiency. Extremely low output current ripple and continuous input current are two other advantages of the proposed converter. Also, the output current can be shared between interleaved modules without using additional current sharing control technique due to charge balance of input and blocking capacitors. All these benefits are obtained without adding any active auxiliary component or using transformers. The experimental results from a prototype of the proposed converter designed for 400-24 V, operating at 0.5 kW, verify the theoretical analysis.

In this study, a new three-level boost converter is introduced which has high voltage gains suitable for photovoltaic applications. Three-level structure has the advantage of low voltage stresses of the switches and diodes. In the proposed converter, semiconductor devices operate under soft-switching conditions which results in low switching losses. It utilises an active clamp circuit with one auxiliary switch to absorb the leakage energy. Therefore, elimination of the voltage spikes across the switches as well as efficiency improvement is achieved. On the other hand, the proposed converter has one magnetic core, and consequently, reduced size. Operating principles of the proposed converter along with its theoretical analysis are presented. Experimental results of a 200 W laboratory prototype for voltage conversion of 40 V/400 V are provided in order to verify the proposed converter performance.