On the noise characteristics of a switching regulator

This paper presents analytical and experimental considerations on the noise generated in the typical switching regulator with two-winding configuration. There are two kinds of surges; one occurs at the instant from ON to OFF of the switching transistor, and the other occurs at the instant from OFF to ON of the transistor. These surges appear as high voltages across the semiconductor elements and decrease their reliabilities. Corresponding to the surge generation, noise voltages appear in the output terminals, and may induce malfunctions of a signal processing equipment connected to the regulator. We analyze these surge nad noise voltages by means of high-frequency equivalent circuits. The analytical results agree well with the experimental ones. Further, as another performance index of the reliability of a power supply, we discuss the suppression feature of the switching regulator against external noise.