A transformerless resonant multilevel DC-DC step-up converter

This paper presents a novel topology of transformerless DC-DC step-up converter based on the association of several resonant sub-circuits in a multilevel configuration. It allows for the interconnection of a generic number of conversion modules, rated both for a fraction of the output voltage and power, in series at the output side and in parallel at the input side. This arrangement is made possible due to the use of coupling capacitors in the series branches of the resonant circuits, which block the DC voltage components amongst the different modules. Large voltage stepping-up ratios are therefore possible, by associating a large number of modules (levels), without compromising the performance, the dimensioning process and the controls of each individual module. Its operating principle is developed and the main dimensioning equations are derived. A model is established to estimate the common mode current in the grounding loop and some techniques to mitigate its magnitude are mentioned. Simulation results are presented and discussed in order to validate the principle, both with a 2-level (100V to 220V) and a 6-level (100V to 680V) DC-DC step-up converter.