A Symmetrical Inductor Current Modulated Buck Converter With Spread-Spectrum Scheme for Low EMI and Low Output Ripple

This work proposes a Symmetrical Inductor Current based Spread-Spectrum Frequency Modulation (SIC-SSFM) scheme for buck converters, aiming at optimizing both the Electromagnetic Interference (EMI) and the output voltage ripple. Compared with conventional frequency modulation approach, the proposed symmetrical structure helps minimize the averaged inductor current ripple and thus the output ripple. By utilizing the proposed method, the proposed buck converter eliminates the need for oscillators or any slope compensation, effectively optimizing the quiescent power consumption. The proposed converter supports input and output ranges of 5-40V and 3.3–5V, respectively. It is capable of delivering 2A maximum load while consumes only 8.4μA quiescent current. The measured output ripple is 9-12.5 mV, achieving a peak efficiency of 93.36%, while the measured EMI is reduced by 18.5 dB due to the proposed SIC-SSFM. The active SIC-SSFM circuit occupies an area of 0.06 mm², with a total buck area of 2.32 mm×1.88 mm.