Ageing Platform for EMC Testing

Abstract

Switching power supplies generate electromagnetic interference due to of their inherent design characteristics. Internal switching power supply circuits that generate undesirable emissions that are rich in harmonics can cause electrical interference both internally to the circuit in which the power supply is installed and to other electronic equipment in the vicinity of the emission source. The work of this thesis was to evaluate how ageing could affect the conducted emissions of a device and if with the ageing of the device, the limits regarding conducted emissions, imposed by the Comité International Spécial des Perturbations Radioélectriques continue to comply, otherwise the devices will become non-compliant according to the Community Directive of EMC. The devices tested were switching-mode power supplies, usually used in desktop computers. To start they were under tests for conducted emissions. All the test were done in a proper site and with all the standards that are inherent to such tests. To age the devices a platform were created, the acceleration life condition selected was power cycling. The application of this method leads to an electrical ageing of the equipment and it basically consists in turn the power of the devices under test On and Off repeatedly, during certain period of time. The major advantage is that with the use of this technique the time needed to age an equipment is largely reduced when compared with a normal usage. In the end of the test there was a modification of the spectrum, what indicates that the platform created can change the emissions of the devices under test. By analyzing the results it was verified that the ageing affect these emissions, however it was not enough to make the device noncompliant. According to the results obtained conclusions were taken about how the ageing of a device may lead to an increase in the conducted emissions.