Improving the Efficiency of SiC-Based Synchronous Boost Converter Under Variable Switching Frequency TCM and Different Input/Output Voltage Ratios

Abstract

This article is focused on the design of a high-voltage (800 V) bidirectional boost converter with high efficiency at medium-low power levels. Triangular current mode (TCM) enhances the efficiency of the converter at low power, thanks to soft-switching operation, but it requires variable switching frequency and large current ripple through the inductor. The former can be implemented by using silicon carbide (SiC) mosfet s and the latter can be minimized by using interleaved modules. At low power, TCM requires high switching frequency, a minimum negative inductor current, and a minimum deadtime to obtain zero voltage switching. These values vary for different input/output voltage ratios and must be properly selected to reduce deadtime losses, normally neglected in the literature since it is assumed that they have low impact. However, it can be relevant at high frequencies (especially for devices with high reverse conduction voltage drop, such as SiC mosfet s). In this article, deadtime losses are included in the proposed losses models and the selection of optimum values of deadtime and minimum inductor current to minimize these deadtime losses are analytically evaluated and experimentally validated.