Improving Validation Of Power Supply Re-Rush Performance Through More Accurate Sensing Of AC Line Peaks

Focus:

Switch-mode power supplies that support a wide range of input voltages (up to 277 Vac) in real applications can operate in various ac transient conditions such as voltage sags and surges, dropouts, line frequency deviations, etc. Although these conditions are detailed in power supply specs and replicated with conventional programmable ac sources during qualification, some power supplies that pass extensive qualification tests may still have a significant failure rate in the field due to ac transients associated with the so-called re-rush event. This article examines the impact of the ac peak voltage detection accuracy on replicating the worst-case re-rush condition and discusses shortcomings of the direct input voltage sensing technique. It then presents a simple technique based on voltage derivative sensing for improving the accuracy of such detection.

What you’ll learn:

• How to accurately detect peak ac line voltage when testing power supply susceptibility to re-rush currents

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Author & Publication:

Viktor Vogman, Olympia, Wash., How2Power Today, Mar 14 2025

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