Impact of switching interaction on FWD chip size selection for an asynchronous boost converter

Abstract

This paper investigates how switching interaction between power semiconductor devices affects the selection of free-wheeling diode chip size in asynchronous boost converters. Coupled switching losses were measured through double pulse tests, and conduction losses were characterized independently. The results reveal that increasing the FWD chip size reduces its conduction loss, but can significantly increase the overall switching losses due to interaction with the power switch, especially when the switch is small. Furthermore, FWD chip size selection for the efficiency depends strongly on system operating conditions such as switching frequency, duty ratio, input voltage, and temperature. The analysis shows that a simplified loss calculation ignoring device interaction can result in significant errors in FWD selection, particularly at high switching frequencies, voltages, or temperatures, which are increasingly relevant with the adoption of SiC technology. These results demonstrate that switching losses must be measured with the actual device pair to ensure energy-efficient converter design.