Non-isolated input-series–output-parallel three-level buck converter

Abstract

This paper proposes a non-isolated input-series–output-parallel (ISOP) three-level buck converter. A theoretical analysis indicates that it has a large step-down ratio and low component voltage stress with the input and output terminals sharing the same ground. An automatic current-balancing mechanism is revealed, and it indicates that the parasitic parameters and inductance variations influence the automatic current-balancing effect. Thus, current-balance control is necessary. Considering that the proposed topology has an ISOP configuration, two voltage-balance control strategies are proposed to realize input capacitor voltage balancing and output inductor current balancing. One is implemented based on a two-loop configuration with an output voltage loop and a voltage-balance loop. The other is developed based on a three-loop configuration by adding one inner current loop on the two-loop configuration. Finally, experimental results have been given to verify both the proposed converter and voltage-balance control.