Output Capacitance Calculations Theory

Once the filter inductance has been calculated, the value of the output filter capacitor is calculated to meet the output ripple requirements. An electrolytic capacitor can he modeled as a series connection of an inductance, a resistance, and a capacitance. To provide good filtering, the ripple frequency must be far below the frequencies at which the series inductance becomes important: so, the two components of interest are the capacitance and the effective series resistance (ESR). The maximum ESR is calculated according to the relation between the specified peak-to-peak ripple voltage and peak-to-peak ripple current.