Power-Loss and Efficiency Comparison of SiC C3M0075120D and GaN GS66508B in a DC–DC Buck Converter

The growing demand for high-efficiency power conversion has accelerated adoption of wide-bandgap (WBG) devices in DC-DC converters. While SiC and GaN MOSFETs outperform conventional silicon, direct quantitative comparisons under identical buck-converter conditions remain an area of active investigation. This simulation-based study investigates power losses and estimated efficiency of SiC C3M0075120D (1200 V, 75 m ) and GaN GS66508B (650 V, 50 m ) in a 200 V-to-100 V, 50 kHz DC-DC buck converter under identical loads (5 A and 10 A). Using LTspice simulations with manufacturer-supplied models and Double Pulse Test methodology for loss separation, the study explicitly distinguishes switching and conduction losses under fixed operating conditions, providing validated simulation-based quantification for these specific devices. The results indicate that for the GaN device achieves lower modeled total losses than the SiC device at 10 A (6.85 W vs. 17.05 W) and attains higher simulated estimated converter efficiency (99.31% vs. 98.25% at full load). For the two specific devices and simulated operating conditions examined, switching loss remains the dominant loss mechanism at 50 kHz. A frequency sensitivity analysis from 50 to 500 kHz reveals that the GaN device maintains approximately 60% lower losses across the frequency range, with absolute savings increasing from 10.2 W to 91.2 W. These findings apply specifically to the investigated devices and operating conditions, and the comparison involves devices with different voltage ratings. The methodology demonstrates the utility of LTspice as a pre-prototyping tool for WBG converter development, although experimental validation remains necessary to confirm estimated efficiency figures.