Common-mode noise generation in a DC-to-DC converter

Analytical and experimental considerations on the common-mode noise in a dc-to-dc converter are discussed. Analyzing the mechanism of the commom-mode noise generation by means of a high-frequency equivalent circuit, we estimate the output noise voltage generated during the transistor´s turnon time. This common-mode noise consists mainly of two frequency components distributed in several megahertz. The effects of parasitic parameters on the noise voltage and frequencies are clarified.