One of the fundamental challenges of DC-DC converters is the drop in efficiency at light load conditions. A novel resonant gate driver structure is proposed to reduce the gate driver loss by introducing an energy storage component to the gate of power switches. A new multi-phase output inductor network with both positively coupled inductors and negatively coupled inductors is also discussed for phase shedding/segmentation applications. A 100 MHz two-phase, four-segment CMOS DC-DC converter with resonant gate driver and the new inductor network is implemented employing hysteresis controller and an open loop delay chain with automatic duty ratio corrector. Complete close loop measurement results show 77.8% peak efficiency at 4 V/3 V conversion and 5% efficiency improvement using resonant gate drivers is achieved at 1 V output. The output efficiency follows the peak value when load current changes from 0.1 A to 2 A with phase shedding/segmentation technique.