An Air-Core Coupled-Inductor Based Dual-Phase Output Stage for Point-of-Load Converters

This paper presents a high-switching-frequency and high-efficiency dual-phase output stage for Point-of-Load (POL) converters. The proposed design is based on a novel air-core coupled-inductor that exhibits variable inductance. Specifically, the proposed coupled-inductor exhibits different equivalent inductance within one switching cycle, thus offering combined merits of fast transient response, small current ripple, and good current balance. The prototype output stage, realized in a 180nm CMOS process, operates up to 30MHz and features the input voltage range of 1.8-3.6V and the output voltage range of 0.6-3.3V. A maximum output power of 6.6W and a peak power efficiency of 88.0% are achieved. Further, in comparison with the conventional approaches, the proposed dual-phase output stage achieves 13% smaller current ripple and 54% faster transient response.