Specifying control of immunity to power line switching transients

Theoretical and experimental investigation reveals discrepancies between common spike immunity requirements and real switching transients. In particular, excessively low source impedance forces unnecessary over-design of EMI filters. A test method using a LISN (line impedance stabilisation network) and switched high current load is investigated as an alternative transient generator, and the effect on filter-design is noted. This test method has dual advantages: a) it simulates real world transients in both amplitude, duration and source impedance, and b) it uses commonly available EMI test equipment and requires no expensive single application acquisitions