A new switching frequency modulation scheme for EMI reduction in multiconverter topology J. Mon, J. Gago, D. González, J. Balcells, R. Fernández, I. Gil Departament d’Enginyeria Electrònica, Universitat Politècnica de Catalunya. c\Colom nº 1 Terrassa, Spain Tel.: +34 / (93) – 739.89.36. Fax: +34 / (93) – 739.80.16. E-Mail: jmon@eel.upc.edu Acknowledgements This research is supported by “Ministerio de Ciencia e Innovación de España”, in the frame of the project TEC2007-61582. Keywords EMC/EMI, Interleaved Converters, Power supply, Switched-mode power supply. Abstract This paper presents a modulation scheme in order to reduce conducted Electromagnetic Interference (EMI) generated by modular power converters with parallel topology. The proposed scheme is based on a combination of interleaving and Switching Frequency Modulation (SFM) techniques. The objective of this modulation scheme is to cancel certain harmonics of EMI and to reduce the amplitude of the remaining harmonics. The proposed scheme has been implemented in a field programmable gate array and a four channel parallel buck converter has been used in order to verify it. A significant EMI reduction has been obtained in comparison to use the interleaving and Switching Frequency Modulation separately. Introduction Power converters operate with switching signals which present high currents and voltages in periods of few microseconds. As a result, these kind of systems generate conducted Electromagnetic Interferences (EMI) in the power lines that can affect other circuits or devices. These interferences can be propagated through power and signal wires or coupling paths by electric and/or magnetic field. Consequently, the reduction of conducted EMI generated by power converters has become an important issue to study. In order to reduce conducted EMI several methods have been proposed in literature. The Switching Frequency Modulation (SFM) technique is a well-known method for conducted EMI reduction in power converters [1-6]. This technique consists of varying the switching frequency in order to generate a distribution of the energy of the interference harmonics in side-bands. This effect reduces the amplitude of each interference harmonics. In the last years, the SFM technique has been studied in different kind of centralized power systems, such as switching mode power supplies (SMPS) [1,2], resonant ballast [3], domestic induction cooking appliances [4], active filters [5] or drive motor [6]. However, according author’s knowledge, in modular or distributed power systems (Fig. 1) the Switching Frequency Modulation technique has not been deeply evaluated. The modular or distributed power systems present several advantages in comparison with centralized power systems, such as redundancy, better sharing of load currents and dynamic behaviour [7]. On the other hand, these kinds of systems have an important relevance in power supply industry. The modular power supplies with parallel topology (Fig. 1) are used in microprocessors powers supplies, which require high current level with low voltage level [7]. A new switching frequency modulation scheme for EMI reduction in multiconverter topology MON Juan EPE 2009 - Barcelona ISBN: 9789075815009 P.1