For automotive applications there is an increasing demand to miniaturize power electronics circuits and operate at higher temperatures. Active SiC-based devices operate at high frequency which decreases circuit dimensions. Passive components, such as the DC-BUS capacitor, must complement new SiC technology. In this study the high frequency performance of DC-BUS capacitors in a DC-DC converter was tested. The relationship between ripple voltage and ripple current were explored as a function of switching frequency (fs) and total DC-BUS capacitance. The DC-BUS capacitor's charging and discharging current was independent of the capacitance or switching frequency. The calculated necessary capacitance for DC-BUS capacitor was proportional to 1/fs and 1/fs 2 by assuming constraining condition of ripple voltage and ripple current, respectively. In addition, to minimize the DC-BUS capacitor size, the current density through the capacitor was calculated as proportional to fs and fs 2 by assuming constraining condition of ripple voltage and ripple current, respectively. Therefore, high current density performance will be important to miniaturize power electronic circuits by increasing switching frequency. DC-BUS current and DC-BUS voltage noise increased with increasing switching frequency over a wide frequency range. The benefit of using a multilayer ceramic capacitor (MLCC) to reduce noise was demonstrated.