Noise Generation in a Forward DC-to-DC Converter

The mechanism of switching-noise generation is examined for the most popular power converter, i.e. the forward dc-to-dc converter. Particularly the output noise voltage generated during the transistor´s turnoff is analyzed by dividing the turnoff time into four sequent states and deriving the corresponding high-frequency equivalent circuits. In these circuits the parameter of transistor´s fall time is also introduced. As the result, not only the influence of the inductive or capacitive parasitic elements on the noise generation but also the relationship between the transistor´s switching speed and the noise voltage are quantitatively clarified.