Analysis of ripple current of an electrolytic capacitor in power factor controller

A large electrolytic capacitor is usually used at the output terminal of power factor control circuits to suppress the high-frequency switching ripple voltage as well as the low-frequency ripple voltage. Due to the equivalent series resistance of the electrolytic capacitor, the capacitor current causes a power loss which increases its temperature and may shorten its life time. It is important therefore to estimate the effective value of the capacitor current accurately. This paper presents a detailed analysis of the ripple current of an electrolytic capacitor in a boost-type power factor control circuit. The ripple current is divided into two components, namely the low-frequency and the high-frequency components. The root-mean-square value of the capacitor current is derived for both components. The analytical results are confirmed by experiments