Analysis and Experimental Evaluation of a Soft Switching Boost Converter with Unbalanced Capacitor Voltage

This paper presents a novel unbalanced capacitor voltage (UCV) soft switching boost converter under full loads range with a simple control scheme. The topology consists of a half bridge switching-leg, filter inductor, and an auxiliary circuit containing one switch and one resonant inductor. It uses the resonance between the parasitic output capacitors in parallel to each active switch and the resonant inductor to achieve zerovoltage-switching. The auxiliary circuit, acting as the resonant tank, is employed just before the main switch is turned on. It has been demonstrated that the controlled unbalancing of series connected output capacitor voltages causes the low side capacitor voltage to be less than half of the output voltage, which creates the necessary condition to achieve soft switching for the low duty ratio and low power loads. The concept is validated experimentally on a 1 kW/200 kHz prototype implemented with silicon carbide (SiC) MOSFET operated within a wide range of duty ratios and load powers. The rated efficiency of the proposed converter is 95.7% as soft switching reduces up to 60% of the total losses when compared with a hard switching converter