A Dithering Technique for Mitigation of Differential Mode Noise of SiC MOSFET Based Buck Converter

One of the significant disadvantages of high frequency power electronics converter is its Electromagnetic Compatibility(EMC). The converters must meet different Electromagnetic interference(EMI) standards, i.e., CISPR, and IEC set by various international bodies for commercialization. Low frequency (150 kHz-2 MHz) conducted emission noise is due to switching harmonics of the converters. High values of high frequency DC bus capacitor are used to reduce Differential Mode (DM) noise. Such high values of DC bus capacitors make the converter bulky. Also, these DC bus capacitors should have a high Self Resonating Frequency (SRF) to absorb DM noise of frequency range 500 kHz-2 MHz. Finding such high value capacitors with high SRF is very much challenging. The present article presents a dithering technique that is very simple to implement in hardware and passes CISPR standards with a minimal amount of DC bus capacitors without compromising the efficiency of the converter. A DC-DC buck converter has been used in this paper for validating the proposed dithering technique. Resolution Band Width (RBW) has been taken 9 kHz while measuring the noise, as per CISPR-11 standards and the proposed technique has been modified according to 9 kHz RBW.