This study presents an interleaved high step-up DC-DC converter based on three-winding high-frequency coupled inductor and voltage multiplier cell (VMC) techniques. The primary and secondary windings of each coupled inductor are inserted in the same phase and the third winding is inserted in the other phase. The VMC in each phase consists of two diodes, two capacitors, the secondary winding of the same phase coupled inductor and the third winding of the other phase coupled inductor. The voltage gain is increased and the output voltage is clamped across the capacitors of the VMCs. Then, the voltage across the power metal oxide semiconductor field effect transistors (MOSFETs) is decreased. The leakage inductance of the coupled inductors controls the output diode falling rate, which alleviates reverse recovery problems. The power MOSFETs are turned-on under zero current switching that helps to conversion efficiency improvement. Three modes of operation named as continuous conduction mode, discontinuous conduction mode and boundary conduction mode are investigated for the proposed converter. The carried mathematical analysis and satisfying operation of the proposed converter are verified via experimental results of an 870 W 60 V-input to 590 V-output laboratory prototype with 95.2% conversion efficiency.

A non-isolated DC-DC converter with high-voltage gain and low-voltage stress across the semiconductors is proposed in this study. The proposed converter consists of n stages of diode-capacitor-inductor (D-C-L) units at the input side and m units of voltage multiplier cells (VMCs) at the output side. Increasing of D-C-L units and VMCs, lead to high-voltage gain at low duty cycle. Lower values of duty cycle will result in increasing of converter controllability and increasing of operation region. Also by increasing of VMCs, the voltage stress across the main switch and other semiconductors is reduced severely. Decreasing of voltage stress across the main switch leads to use a switch with lower R DS-ON that reduces on state losses of the proposed converter. Besides, by decreasing of voltage stress across the diode rectifiers, diodes with less forward voltage drop can be adopted. The circuit performance will be compared with other solutions that were previously proposed for voltage step-up in the terms of voltage gain, main switch voltage stress and number of components. Finally, a 357 V-65.5 W laboratory prototype with 92% conversion efficiency is built in order to prove the satisfying operation of the proposed converter and carried mathematical analysis.

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The thermal diffusivity kd of silicon between - 50°C and 100°C has been obtained by measuring the phase-shift of a thermal wave between two points on a small sample. The relation between the thermal diffusivity and phase-shift is obtained by solving the heat flow equations. The present results agree closely with those obtained by conventional methods.

In this study, a novel developed structure of a converter based on double flying capacitor multi-cell named progressive double flying capacitor multicell (PDFCM) is proposed. The main advantage of this proposed structure compared with DFCM converter is generation of more output voltage levels while having the same number of devices. This novel converter's structure is based on integration of two extended cells between the conventional cells in DFCM converter. PDFCM converter has various structural states which are named based on the number of units, consisting of two extended cells and one conventional cell. These structural states are changing by the increase of levels depending on the number of cells. Thus, the progressive increase of the number of produced levels of proposed converter is because of the increase in the number of the units. In fact, by appropriate selection of the proposed converter states, the number of levels in output voltage will be higher than those of conventional converters. This converter can be controlled either by open-loop, self-balancing or closed-loop methods. In addition, the switching method is based on space vector modulation. The simulation and experimental results confirm the validity and effectiveness of the presented converter.