Design and development of a microcontroller-based Single Input Multiple Outputs (SIMO) power system for off-grid photovoltaic applications

Abstract

Cross-regulation problem and power dissipation due to multiple switching are mostly encountered among single-input multiple outputs (SIMO) converters. In present research, a SIMO flyback converter is designed and developed to evaluate the effect of switching frequency and overcome cross-regulation error. The developed converter system has four output levels of 24 V,12 V,9 V and 5 V and contains minimum number of components with low cost (USD20) and power dissipation (<2%). Ferrite-core transformer is used to generate four output voltage levels. All the four windings are wound around a common core and the developed system provides high efficiency and reduce dissipations. As voltage is applied at the primary coil, a magnetic field is generated around the core due to mutual inductance. The magnetic field strength induced into the core depends on the number of turns, current and voltage in the winding. The percentage error at the outputs of the SIMO converter is more on terminals with less number of windings; the higher the voltage the less the error. The average switching frequency f sw against k (a control parameter for switching frequency) is notably higher with lower k. However, for small k, (i.e. at high switching frequency), the voltage regulation is tighter and more accurate. Therefore, 0.1<k<0.2 has been set and the regulation error are limited to <1%. The switching and control techniques operate at an average switching frequency of 199 kHz with small frequency fluctuations and output voltage ripples around 10 mV (i.e <0.1% of V0) under nominal conditions of Vi=12 V. Efficiencies of 97%, 97.3%, 98.2% and 98.4% have been obtained across the four terminals for 24 V, 12 V, 9 V and 5 V respectively.