Abstract
M.Ing.
In this investigation charge balancing will be investigated from an Electro-Magnetic-
Compatibility perspective. The primary sources of common mode Electro-Magnetic-
Interference in switching converters are the switching nodes. This is mainly due to the
parasitic capacitance between the switching node and the reference earth. Filtering
components that are currently used take up a lot of valuable space resulting in the
products overall size and cost to increase. Combating common mode current at the
source will drastically reduce the size or the need for these large filters. This
investigation will focus on a simple method of reducing common mode noise
(produced by the switching node), of a two wire system, at the source by making use
of a compensating winding which requires very little or no additional space; a buck
converter will be used to illustrate the concept. The investigation will start with an
overview of Electro-Magnetic-Interference and its components (common and
differential mode noise). This investigation will deal with the measurement of
common and differential mode noise as well as general Electro-Magnetic-Interference
measurement. A design of the buck converter and its drive circuit will also be
presented. Reducing the common mode noise by making use of charge balancing
using planar inductors will then be presented. This investigation contains the
theoretical analysis as well as experimental results to validate the theory. The
experiments show encouraging results in using this technique to minimise common
mode noise in switched-mode-power-supplies.