Impact of QSW-ZVS on Input EMI Filter Design in DC-DC Converters

This paper investigates the impact of the Quasi-Square Wave Zero Voltage Switching (QSW-ZVS) technique on the design of passive ElectroMagnetic Interference (EMI) filters for DC-DC Buck converters. A standard design-oriented analysis is conducted, focusing on a single-stage LC EMI filter with a single-resistor shunt damping network Rd-Cd, aiming to minimize the impact of the filter on the small-signal dynamic of the converter. We demonstrate that QSW-ZVS enables a reduction in the size of the damping network of the EMI filter when compared with conventional hard-switching designs. Furthermore, we generalize the proposed analysis to different EMI filter cutoff frequencies, evaluating how the value of the shunt damping capacitance Cd varies when QSW-ZVS is enabled. Both the proposed small-signal model and the design methodology are validated with SIMPLIS simulations under various operating conditions of a DC-DC Buck converter.