Investigation on Relationship between Common Mode Noise and Distribution of Parasitic Capacitance

Abstract

This study investigates the influence of parasitic capacitance on the common mode (CM) noise in a converter. A thermal pad on a switching device is necessary for sufficient heat dissipation. In addition, the thermal pad increases the CM capacitance between the printed circuit board and the ground plane. The parasitic capacitances form CM noise propagation paths. However, which node in the circuit and the corresponding parasitic capacitance influences the CM noise the most and the degree of the parasitic capacitance influence on the CM noise are unclear. In this study, the parasitic capacitance that influences the CM noise in a converter is identified, and the extent to which the parasitic capacitance affects the CM noise is investigated through simulations and experiments.