Ripple Current and Power Load

The key point to remember from this lesson is that transient surge current in power circuits (or just in battery circuits) can overload the capacitor constructional limitations. Some capacitor technologies are more sensitive to the transient then others.

In case that higher power rating of capacitors is needed, a special dedicated “surge/pulse” robust series may be available that can handle such operations better. Usually it is not “just screened” parts, but the inner capacitor construction is ruggedized and provide better safety and reliable when loaded by high inrush current.

The same is valid for a continuous load ripple current, please check the capacitor technology specification and manufacturers recommendation for maximum performance.

Frequency and temperature may also significantly influence the ripple current handling. For example MLCC classs II capacitors are known for a very low ESR … but this is true only at the specification rated conditions i.g. 100kHz. Sometime we need to filter LED backlight circuits in about kilohertz range or by-frequency to telecom in low frequency spectrum such as 260Hz. In these frequencies MLCC class II capacitors may have higher ESR then even electrolytic capacitors due to its high dielectric losses … and it can be surprising for some designers that electrolytics aluminum or tantalum works here better.

If you are not in-depth familiar with frequency, voltage and temperature behavior of capacitor technologies it is always good idea to check leading manufacturers’ simulation tools to see how these technologies behave and what is a maximum ripple current load at the operation conditions.

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