EMC characterization of SMPS devices: circuit and radiated emissions model

Since the efficiency of switched mode power supplies (SMPS) is much higher than that of linear power supplies, this type of supply has gained favor among designers and manufacturers. Switching frequencies extend from tens to hundreds of kilohertz with the result that radiation from circuits carrying switched current is becoming more of a problem. This paper addresses the modeling of the converter section of an SMPS in order to calculate the current distribution and the radiated electromagnetic field. The inhomogeneities in the circuit are by equivalent electrical parameters and a technique is introduced to take into account the fictitious effects on radiation due to the electrostatic terms in the dipole equations. The global approach is validated by comparison of the computed results with those measured for a simple and clearly arranged SMPS experimental setup.