An investigation into the radio frequency emissions from switched mode power supplies and similar switched electronic load controllers operating under various loading conditions

Over recent years Switched Mode Power Supplies (SMPSs) and similar Switched Electronic Load Controllers (SELCs) have become major sources of deterioration of the electromagnetic environment. In many cases when Electromagnetic Compatibility (EMC) tests are performed on such devices, the load conditions during the tests can be significantly different from the actual load conditions that the device operates under in the field. This paper presents the results of Radio Frequency (RF) emission measurements which have been performed on various SMPSs and SELCs to examine the effect of the loading conditions on the RF emissions observed from the devices. Results of this research have led to the drafting of a code of practice for the design of SMPSs and SELCs giving guidance on how to design such devices to ensure good EMC characteristics.