The output of a rectifier is a pulsating dc. By the superposition theorem, this rectifier output can be looked upon as having two different components : a dc and an ac. The direct current is the average value of the pulsating current, averaged over each half cycle of the ac input. The ac component in the output is called the ripple. Ripple is undesirable in most electronic circuits and devices.
The ratio of the root-mean-square value of the ac component to the average value of the dc component in the filtered rectifier output is known as the ripple factor. Ripple factor = \(\cfrac{(rms \,value \,of \,ac \,component )}{(average \,value \,of \,dc \,component)}\) Percentage ripple = ripple factor × 100% This factor mainly decides the effectiveness of a filter circuit in a power supply, i.e., smaller the value of this factor, lesser is the ac component in comparison to the dc component. Hence, more effective is the filter.
