Design and Experimental Measurement of EMI Reduction Techniques for Integrated Switching DC/DC Converters

This paper presents the design and verification of electromagnetic interference (EMI) reduction techniques for switching dc/dc converters. A 48-V dc/dc converter for electric/hybrid cars is considered as an application case study. An EMI filter with a very low inductor value is designed to reduce the overvoltage issues. The proposed design procedure takes into account the converter impedance and the cable model in order to avoid the state-of-the-art tendency of oversizing the filter components. Thus, the filter implementation is simplified and its EMI reduction capability is kept unaltered. Measurements of near EM field in anechoic room show that, using a low switching frequency for the dc/dc converter, the EMI problem is shifted from radiated to conducted emissions. A SKIP-mode modulation technique is implemented to control the converter output and also to reduce the conducted EMI, as shown by CAD simulations and experimental measurements. In addition, a soft-start technique, which reduces by three times the currents' spikes, is integrated into the dc/dc converter to minimize the EMI at the car's starting.