A boost-switched capacitor-inverter with a multilevel waveform

Two structures, a switched-capacitor (SC)-based boost converter and a two-level inverter, are connected in cascade. The DC 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 closed 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 (THD). Simulations and experiments on a prototype with a five-level output confirm the theoretical analysis.