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A simple graph with four nodes and eleven branches is defined. Its branches are filled in different ways with passive elements (capacitors, inductors, diodes) or replaced by shortcircuits in order to get potential voltage step-up switching cells. These cells are inserted in boost converter, obtaining thus non-isolated power electronics circuits with a very high dc gain. Such circuits are necessary today in the green energy systems. The proposed circuits feature a lower voltage stress on its semiconductors (both switch and diodes) than that on the equivalent devices of a boost stage. A state-space-based dc and ac analysis allows for deriving the dc gain, the switches voltage and current stresses, and the frequency characteristics of the obtained converters. The steady-state analysis is performed for both the continuous and discontinuous conduction mode operations. The converters belonging to the new family are compared between them and then compared with available solutions of similar complexity as defined by the component count. Simulation and experimental results confirm the theoretical equations. [ABSTRACT FROM PUBLISHER]

Two structures, a switched-capacitor (SC)-based boost converter and a two-level inverter, are connected in cascade. The de multilevel voltage of the first stage becomes the input voltage of the classical inverter, resulting in a staircase waveform for the inverter output voltage. Such a multilevel waveform is close to a sinusoid; its harmonics content can be reduced by multiplying the stage number of the SC converter. The output low-pass filter, customary after a two-level inverter, becomes obsolete, resulting in a small size of the system, as the SC circuit can be miniaturized. Both stages are operated at a high switching frequency, resulting in a high-frequency inverter output, as required by some industrial applications. A Fourier analysis of the output waveform is performed. The design is optimized with reference to the nominal duty-cycle for obtaining the minimum total harmonic distortion. Simulations and experiments on two prototypes, one with a five-level output and one with a seven-level output, confirm the theoretical analysis. [ABSTRACT FROM AUTHOR]

A detailed analysis and optimized-oriented design of a family of three-level soft-switching converters is presented. The zero-voltage-switching (ZVS) of the outer switches and zero-cur- rent-switching (ZCS) of the inner switches is realized by employing a pulse-width-modulation (PWM) phase-shift control and a secondary-assisted passive snubber. The switching operation is discussed by comparing the results produced by the use of different passive snubbers (the author's original one and literature-available ones). The voltage on the rectifier diodes is clamped at a reasonable value, specific to each one of the six snubbers taken into consideration. The voltage stress on each transistor is reduced to half of the input voltage. Lower rated transistors and rectifier diodes can be used, thus reducing the conduction losses. Before turning on/off the inner switches, the snubber's capacitor voltage determines the fall of the primary current to zero, thus avoiding wasteful energy circulation and assuring ZCS. The snubber's energy is recuperated to the load. The outcome of these improvements is a high efficiency in energy processing. Soft-switching-oriented constraints on the converter parameters are expressed as implicit equations, whose graphical solution permits the optimized design of the parameters in order to ensure ZVZCS. A comparative analysis of the effective duty cycle and the boost effect of it, due to the use of the secondary snubber, is performed. The influence of the choices of the parameters values on the regulation capability is pointed out. Experimental results prove the expected high performances of the optimized converters. [ABSTRACT FROM AUTHOR]