Note that the ripple current is made up of the light-blue peaks shown in the waveform provided on this slide. They occur when the load voltage—the light green waveform—falls to less than the rectified AC input voltage, the purple waveform. In this variation in load voltage, the ripple voltage causes the ripple current to flow in the capacitor. Understanding ripple current is key to the successful application of aluminum electrolytic capacitors. While in a linear power supply the ripple current is entirely from rectification of the power line AC mains voltage, in switching power supplies there is also ripple current from the high-frequency switching in the DC to DC converter. The ripple current heats the capacitor and shortens the capacitor’s life. Some important factors to consider are how much ripple current a capacitor can withstand and how long it would last.