High Frequency, Multiple output Flyback Transformer Design for TOP-Switch Power Supplies

Abstract

Switching mode power supply is without doubt an important subassembly for almost all electronic equipments. Due to lower cost, smaller size and high efficiency, flyback is the mostly preferred converter topology for lower power levels. Being the most critical part of SMPS, the transformer always requires extra care while designing. This paper presents a simple, quick and efficient design procedure for flyback transformer used in TOPSwitch power supplies. Transformer design is the biggest stumbling block in TOPSwitch flyback power supplies. Flyback transformers are different from the normal transformer as the energy is stored in the core and the current never flows in the primary and secondary windings simultaneously. Presented design procedure requires iteration through a set of design equations and can be effectively utilized for continuous as well as the discontinuous mode. A new parameter, the ratio of primary ripple current to peak current (KRP), is introduced to describe the TOPSwitch drain current waveform shape and simplify subsequent calculations such as RMS current and AC flux density.