Е-Публикации
Технически университет - София

Abstract: This study presents a sensitivity analysis of a SEPIC (Single-Ended Primary Inductance Converter) DC-DC converter, to assess the impact of variations in the coupling capacitance within a standard commercial step above and below the designed nominal value. The analysis is based on mathematical modeling and frequency simulation in MATLAB/Simulink, tracking the impact of capacitive instability on the dynamic stability, resonant behavior, and electromagnetic emission (EMI) of the system. The methodology involves injecting a single current signal into critical nodes of the circuit with subsequent spectral analysis of the voltage response. The obtained results allow the identification of frequency intervals in which capacitance variations lead to the formation of unwanted resonant peaks, increased output voltage ripple, and impaired filtration of high-frequency interference. The study demonstrates that even small deviations from the nominal value of the coupling capacitor, within factory tolerances, can cause significant changes in the electrical behavior of the converter. This highlights the need for a conservative approach to passive component selection and the inclusion of small-signal analysis early in the design process, especially in applications requiring low noise and high EMC.

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