A 24V-to-1.8V Low Input Current Ripple SC Hybrid Converter with Conducted EMI Noise Suppression Mechanism for Automobile Application

The single-stage 24 V -to- 1 V buck converter can effectively reduce the size of the power module, but its excessive input current ripple will aggravate conducted electromagnetic interference (EMI) noise [1] –[5]. To meet the CISPR 25 standard, large-capacity EMI filters consisting of one inductor and two capacitors are often used, but this takes up a larger printed circuit board (PCB), thereby reducing power density. Double step-down (DSD) converters [1] are suitable for low conversion ratios ($\mathrm{CR}=\mathrm{V}_{\mathrm{o}} / \mathrm{V}_{\mathrm{IN}}$), but suffer from large input current ripple $\left(\Delta I_{\mathbb{I N}}\right)$, equal to $\Delta \mathrm{I}_{\mathrm{L} 1}$ during $\Phi_{1}$ (upper right of Fig. 1). I IN ripple will increase at heavy loads, exacerbating conducted EMI noise. Although the inductor L is magnetized and I<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</inf> is evenly divided into three paths during $\Phi 1$, one of which is powered by $\mathrm{V}_{\mathrm{IN}}$ in the DPSC converter [3] and I<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</inf> is almost equal to lo when CR is 1/24 (middle left). A significant increase in $\Delta l \mathrm{ln}$ at heavy loads will also increase EMI noise effects. In the upper right of Fig. 1, [3] can effectively reduce the voltage variation on each switching node, but the significant voltage variation difference between opposite nodes makes it difficult to cancel the EMI noise.