Autor: Marko Scherf

Following general technology trends, power supplies constantly have to become more effi-cient and smaller in size. Because of their impact on the efficiency and power density, magnetic components are key parts of a power supply system. Unlike other components, magnetics are widely free to be configured by the designer. There are a lot of interactions between the magnetics and their related electrical circuits, that’s why the system optimization is an iterative process. Of course, the magnetics’ elec-trical characteristics have influence on the circuit behavior. But the power supply concept, e.g. the number of power stages and the converter topologies as well as circuit parameters like switching frequency are affecting the design and characteristics of the magnetics, thus their size and thermal characteristics. Main topic of this thesis is the investigation of the impact of circuit parameters on the magnetic parts in popular forward converter topologies. The general approach is on the one hand the computer-assisted design of a bunch of precise transformers and inductors for real application boundary conditions. The key is the opti-mization by a precise calculation of core and winding losses. On the other hand, a more theoretic analysis using numeric data is accomplished. The investigations are split in two main parts. One deals with the influence of voltage ranges and duty cycle reserves on the transformer and output inductor for two comparative con-verter topologies. The basis is a distinction of cases, derived from different power supply concepts. A strict differentiation between varying static voltage ranges and a voltage reserve for short-term action is done. The other part is an elaboration of the magnetics’ size and power loss dependence on the switching frequency. Considering the application of state-of-the-art power magnetic materials, the today’s potential and limits in magnetics optimization by adjusting the frequency is shown. Additionally, general principles are explored and an analytic method for a better prediction of the frequency dependence is introduced. Intention of the thesis is to provide important background knowledge especially for designers of SMPS circuits and magnetics. It is not intended to displace a proper magnetics design software tool, but to allow a more target-oriented work with it.