A high-efficiency 12V -input 1V-1.8V -output DC-DC converter with wide output current range is highly desirable in energy-efficient portable devices (e.g., laptops) and automotive applications. textIn such applications, the considerably small duty ratio D(D < 0.1) and power switches' high voltage stress of the conventional buck converter brings significant efficiency penalty (Fig. 11.10.1, top left). Both industry and academia have developed many hybrid DC-DC converter topologies to overcome these problems [1-6]. The double step-down (DSD) converter, shown in Fig. 11.10.1 (top right), is the most popular solution [2-4] for this application. textIn the DSD converter, the flying capacitor CF sustains half of VIN, relaxing the voltage stress of the switches to VIN/2 and enlarging the duty ratio D. However, the two inductors must provide all the output current, thus leading to a large inductor DCR loss. To reduce such loss, [5] proposed a dual-path hybrid buck (2textPHB) converter (Fig. 11.10.1, bottom left), in which the flying capacitor CF sustains the voltage VOUT and provides an additional output current path. However, the small duty ratio and switches' high voltage stress problems are still significant in the 2textPHB converter. To further enlarge the duty ratio and reduce the voltage stress of the switches, this paper proposes a dual-inductor quad-path hybrid buck (2L4textPHB) converter, as presented in Fig. 11.10.1 (bottom right). The 2L4PHB inherits the strengths of DSD and 2textPHB converter topologies, where the flying capacitor CF0 sustains half of VIN, thus relaxing the voltage stress of the switches. textIn addition, both CF1 and CF2 sustain the voltage VOUT and provide additional output current paths, subsequently further reducing the inductor DCR loss. Among the structures shown in Fig. 11.10.1, it has the largest D ( VCR =D/2(1+D), VCR < 1/6), the smallest average inductor current (iL,avg=iLoad/2(1+D)), and the smallest voltage stress of the switches (VX1,2=0 textor VIN/2-VOUT) when compared with the different topologies mentioned above. Furthermore, 2L4textPHB also owns inherent inductor current balance characteristic.