Interleaved step-down converter with capacitor-diode voltage splitter and minimum switches for low current ripple and extra-low voltage ratio

Abstract

This paper proposes an interleaved step-down converter (ISDC) with a capacitor-diode voltage splitter. Even though the ISDC only utilizes two active switches, it can significantly step down a high input voltage to a much lower level and achieve interleaved current at output and continuous current at input without using an extreme duty ratio. In addition, the ISDC is capable of sharing output current equally between two interleaved paths by controlling the two switches. Therefore, the ISDC has lower current ripples and reduces EMI noise. The ISDC can be easily expanded only by adopting capacitors and diodes for a much higher conversion ratio, avoiding using any active switch. A comprehensive analysis of ISDC is presented, including operation principle, steady-state analysis, design consideration, expendability of the power stage, and converter comparison. A prototype of 500 W is fulfilled to deal with 400-V input and 24-V output, which has verified the accuracy of the theoretical analysis and validated the converter. Experimental results demonstrate that the ISDC achieves a peak efficiency of 92.74% at 350 W and 92.09% at full load. If synchronous rectifiers are employed, the peak efficiency can be up to 94.73%.