Abstract
Electromagnetic interference (EMI) is one of the major problems of switching power converters. This paper is devoted to switching frequency modulation used for conducted EMI suppression in switching power converters. Comprehensive theoretical analysis of switching power converter conducted EMI spectrum and EMI attenuation due the use of traditional ramp and multislope ramp modulation waveforms is presented. Expressions to calculate EMI spectrum and attenuation are derived. Optimization procedure of the multislope ramp modulation waveform is proposed to get maximum benefits from switching frequency modulation for EMI reduction. Experimental verification is also performed to prove that the optimized multislope ramp modulation waveform is very useful solution for effective EMI reduction in switching power converters.
Highlights
Switching power converters (SPC) used in many electronic devices for electric power conversion are noticeable sources of electromagnetic interference (EMI) which can deteriorate normal operation of other electronic equipment
Benefits of periodic switching frequency modulation (SFM) for EMI reduction can be significantly reduced due to amplitude modulation of SPC currents caused by SFM [8]
The amplitude modulation leads to EMI spectrum sidebands distortion and asymmetry with respect to central switching frequency fsw0 and EMI attenuation is lower than expected for the given value of modulation index [8], [9]
Summary
Switching power converters (SPC) used in many electronic devices for electric power conversion are noticeable sources of electromagnetic interference (EMI) which can deteriorate normal operation of other electronic equipment. EMI both conducted and radiated must be reduced in order to meet international electromagnetic compatibility standards (e.g. CISPR 22) requirements. Benefits of periodic SFM for EMI reduction can be significantly reduced due to amplitude modulation of SPC currents caused by SFM [8]. The amplitude modulation leads to EMI spectrum sidebands distortion and asymmetry with respect to central switching frequency fsw0 and EMI attenuation is lower than expected for the given value of modulation index [8], [9]. In order to increase effectiveness of SFM for EMI reduction in SPC (especially for higher values of ∆fsw), multislope ramp modulating waveform (MRMW) was proposed by S.
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