Analytical Optimization of Nonsaturated Thermally Limited High-Frequency Transformer/Inductor Design Considering Discreteness of Design Variables

Abstract

This article proposes an analytical design methodology for nonsaturated thermally limited high-frequency transformers/inductors with the objective of minimum core size and minimum power loss. The major challenge of analytical design methodologies is to simultaneously retain the optimality of design results, simplicity/ease of use, and generality of design methodologies. Most of the reported analytical methodologies have a limitation on optimality due to neglect of discreteness of design variables and have limitations on simplicity and generality because of a complicated winding loss model with the consideration of eddy current effects. To address these limitations, a further optimization process considering discreteness of design variables is proposed to improve the optimality of the design results. A concept of an effective ac resistance factor in terms of all windings is proposed to model the winding loss in a simple and general way so that simplicity and generality of the design methodology are ensured. To illustrate the methodology and its improvement on optimality, the methodology is used to design a 150-W 100-kHz forward transformer and is compared with the methodology without further optimization. Theoretical calculations and experiments both indicate a decrease of about 5 °C of the methodology in this article compared with the methodology without further optimization.