Evaluation of the Sources Reconstruction Technique Applied to Magnetic Field Measurement in Power Electronic Circuits

Power electronic equipment has to comply with many different regulations. Some of them impose strict limits on the radiated and conducted noise that the equipment can generate. In the case of switching mode power supplies, high frequency switching waveforms combine with high voltage and current levels to produce electromagnetic (EM) noise. Conducted noise can be minimized by means of an EMI filter, which can be designed more or less independently from the rest of the power system and usually it achieves success in keeping conducted noise levels below the limits. That is not the case of radiated noise, as it strongly depends on circuit layout, parasitic effects and component placement. In consequence, it is very difficult both to make an 'a priori' estimation of radiation phenomena which can arise during the EMI compliance test and to provide simple and direct solutions in case of need. Moreover, EMI measurements have to be carried out in an anechoic chamber, which is a very expensive resource. In consequence, it is apparent that radiated noise can increase both design time and development cost of a power electronic circuit. In order to solve these problems, an EM sources reconstruction method (SRM) and a 3D scanning system have been recently proposed with a twofold objective: to allow engineers to simplify the EMI measurement procedure and to identify noise sources in the circuit. A review of the method is made in this paper, and it is tested by means of a low power boost converter and a simple radiating structure (a 10 cm x 10 cm loop square). This loop could be an imaginary radiating track present in a nonoptimized PCB layout. Analytical data and experimental results are used to evaluate the scan and reconstruction system proposed. Finally, a short electric dipole is also analyzed in order to test the influence of intense electric fields over the proposed diagnosis method.