Digitally controlled switching converter with automatic multimode switching

This paper presents a multimode digital controller with dead-time self-exploration (DTSE) for synchronous buck converters that simultaneously achieves high efficiency and a fast transient response. The automatic mode switching technique uses the duty-cycle command to determine multimode operation without sensing any current signals. The DTSE algorithm is used to minimize the steady-state duty-cycle command to maximize the converter efficiency. During load transients, a nonlinear control mode is employed to reduce the transient response. The proposed digital controller is fabricated in a CMOS 0.18-μm process. The experimental results for a 1.2-V output voltage show that the measured power efficiency is higher than 85% for a load range of 10-600 mA and that the measured transient response is improved by 28% compared to that of the traditional voltage-mode converter.