ABSTRACT
A number of analog control circuits have been replaced by digital control circuits in power stations and substations in Japan since the middle of the 1980s. The same is for any industrial products such as an automobile, and for home appliances, because of the advancement of digital circuit technologies. At the same time, electromagnetic compatibility (EMC) environments are becoming a significant problem for the digital circuits that are very sensitive to high-frequency electromagnetic waves such as switching and lightning surges.
