A Three-Mode Power Converter Achieving 94.6% Peak Efficiency and Seamless Four-Quadrant Operation

This article introduces a three-mode single-inductor four-quadrant converter (SIFQC) designed for electrochromic (EC) smart window applications. The proposed design introduces a unified single-inductor topology that intrinsically synthesizes bidirectional buck and bidirectional inverting buck characteristics, achieving full four-quadrant operation without redundant magnetic components. A triple-mode control scheme, bidirectional buck, bidirectional inverting buck, and auxiliary transition mode, enables seamless mode switching and smooth zero-crossing of both voltage and current. The proposed converter supports 5–12-V input, −5- to +5-V output and −3- to +3-A load current. A dual-loop feedback control scheme enhances transient performance and ensures system stability. Fabricated in a 0.18-$\mu $m BCD process, the converter achieves a peak efficiency of 94.6% at$\mathbf {V_{IN}} =10$V,$\mathbf {V_{O}} = +5$V, and$\mathbf {I_{O}} = +900$mA. Measurements confirm full polarity reversal in both voltage and current, validating four-quadrant operation.