Capacitator - Non-ideal Behavior - Ripple Current

Ripple Current

Ripple current is the AC component of an applied source (often a switched-mode power supply) (whose frequency may be constant or varying). Ripple current causes heat to be generated within the capacitor due to the dielectric losses caused by the changing field strength together with the current flow across the slightly resistive supply lines or the electrolyte in the capacitor. The equivalent series resistance (ESR) is the amount of internal series resistance one would add to a perfect capacitor to model this. Some types of capacitors, primarily tantalum and aluminum electrolytic capacitors, as well as some film capacitors have a specified rating value for maximum ripple current.

• Tantalum electrolytic capacitors with solid manganese dioxide electrolyte are limited by ripple current and generally have the highest ESR ratings in the capacitor family. Exceeding their ripple limits can lead to shorts and burning parts.
• Aluminium electrolytic capacitors, the most common type of electrolytic, suffer a shortening of life expectancy at higher ripple currents. If ripple current exceeds the rated value of the capacitor, it tends to result in explosive failure.
• Ceramic capacitors generally have no ripple current limitation and have some of the lowest ESR ratings.
• Film capacitors have very low ESR ratings but exceeding rated ripple current may cause degradation failures.