The ripple is defined as the percentage residual component of an AC voltage
superimposed on the rectified and smoothed DC voltage. The residual ripple is a dimensionless value which is calculated from the quotient of the superimposed residual voltage to the DC voltage. The residual ripple is given as a percentage.effort of the filter circuit, a residual AC voltage component always remains on the smoothed DC voltage. This superimposed AC voltage is used to determine the residual ripple.