An IAOT controlled current-mode buck converter with RC-based inductor current sensor

摘要

An improved adaptive-on-time (IAOT) controlled current mode buck converter with RC-based current-sensing circuit and internal soft-start property is presented in this paper. First, the inductor current is sensed by a resistor-capacitor (RC) network, which can fully sense the trend of inductor current with high accuracy. Second, an IAOT control circuit is used to realize the on-time of the power switch adaptively changing with the operation conditions. In addition, the overshoot (undershoot) voltages are reduced by making TON adaptively shorter (longer) during the unloading (loading) transient due to the IAOT control. Third, soft start operation protects the circuit from large in-rush current during startup of the converter. Fourth, the proposed buck converter was implemented with standard 0.18-μm CMOS process. Simulation outcomes have shown an input voltage of 5 V, when the output voltage is ranging from 1.2 V to 3.6 V, with a maximum conversion efficiency of 98% (heavy loads) and 94% (light loads), making the buck converter quite useful in power management ICs.