Balanced buck-boost switching converter to reduce common-mode conducted noise

Because conventional switching converters have been usually using unbalanced circuit topologies, parasitic capacitance between the drain of a MOSFET switch and the frame ground through its heat sink may generate the common-mode conducted noise. The authors have proposed a balanced switching converter circuit, which is an effective way to reduce the common-mode conducted noise. As an example, a boost converter version of the balanced switching converter was presented and the mechanism of the common-mode noise reduction was explained using equivalent circuits. In this paper, the concept of the balanced switching converter is applied to a buck-boost converter. The common-mode noise reduction is confirmed by experiments using a current probe. The normal-mode noise is also measured and their sum is compared with the conducted noise obtained by using LISN. The mechanism of the common-mode noise reduction is explained using equivalent circuits.