Online Efficiency Optimization of a Closed-Loop Controlled SiC-Based Boost Converter

This paper presents an online optimization strategy for a silicon-carbide (SiC) based Boost converter where the converter switching frequency and dead times are adjusted to set the peak synchronous-rectifier (SR) turn-off current so that zero-voltage switching quasi-square-wave (ZVS-QSW) operation is achieved at any given operating point while minimizing inductor current ripple. The optimal converter switching frequency and dead times are determined based on sensed converter input/output voltages and inductor current using multidimensional parametric curve fit. These timing parameters are applied to the converter in a low-bandwidth feed-forward path operating in conjunction with closed-loop regulation of the converter output voltage. Experimental validation of the online optimization strategy is carried out on a 10kW, 600V converter prototype, demonstrating a close match between analytically computed and curve-fit based switching frequency and dead times over wide ranges of operating points. The proposed approach enables operation of the converter with efficiencies greater than 97.5% for input voltages ranging from 200V to 400V, conversion ratios up to 2.5, and power levels between 2kW and 8kW.