AC harmonics effects on small external power supplies (wall warts)

This paper reports on tests performed to determine the response of common low voltage power supplies when their AC power feed is distorted by various types and levels of harmonic distortion. Such distortion could be a possible form of IEMI attack on a facility. It is found that switched mode power supplies are immune to such attacks, but rectifier type supplies are very susceptible, if the distortion is not symmetrical.