Electronic – Hold-up time in SMPS


I know the definition of Hold-up time in SMPS, and how to calculate the bulk capacitor. But I am wondering if someone can explain me how we define the hold-up time (sometimes 10ms, sometimes 16ms,…)? is it based on a standard?
and why we need the hold-up time? what happen if we dont have it

Best Answer

There are standards that indirectly define hold-up times.

The standard IEC 61000-4-11 Voltage dips, short interruptions and voltage variations immunity tests indirectly defines hold-up time when the product has to satisfy performance criteria A.
This document shows some tests (e.g. voltage dip of 40% of 20 ms duration or voltage interruption of 60 ms duration).

For medical devices, the standard IEC 60601-1 applies.
See this document for some durations of voltage dips and interrupts.