Current-mode adaptively hysteretic control for buck converters with fast transient response and improved output regulation

Abstract

This paper presents a current-mode adaptively hysteretic control (CMAHC) technique to achieve the fast transient response for DC-DC buck converters. A complementary full range current sensor comprising of chargingpath and discharging-path sensing transistors is proposed to track the inductor current seamlessly. With the proposed current-mode adaptively hysteretic topology, the inductor current is continuously monitored, and the adaptively hysteretic threshold is dynamically adjusted according to the feedback information comes from the output voltage level. Therefore, a fast load-transient response can be achieved. Besides, the output regulation performance is also improved by the proposed dynamic current-scaling circuitry (DCSC). Moreover, the proposed CMAHC topology can be used in a nearly zero RESR design configuration. The prototype fabricated using TSMC 0.25μm CMOS process occupies the area of 1.78mm2 including all bonding pads. Experimental results show that the output voltage ripple is smaller than 30mV over a wide loading current from 0 mA to 500 mA with maximum power conversion efficiency higher than 90%. The recovery time from light to heavy load (100 to 500 mA) is smaller than 5μs.