A Novel Buck Converter with Constant Frequency Controlled Technique

This paper presents a buck converter with a novel constant frequency controlled technique, which employs the proposed frequency detector and adaptive on-time control (AOT) logic to lock the switching frequency. The control scheme, design concept, and circuit realization are presented. In contrast to a complex phase lock loop (PLL), the proposed scheme is easy to implement. With this novel technique, a buck converter is designed to produce an output voltage of 1.0-2.5 V at the input voltage of 3.0-3.6 V and the maximum load current of 500 mA. The proposed scheme was verified using SIMPLIS and MathCAD. The simulation results show that the switching frequency variation is less than 1% at an output voltage of 1.0-2.5 V. Furthermore, the recovery time is less than 2 mu s for a step-up and step-down load transient. The circuit will be fabricated using UMC 0.18 mu m 1P6M CMOS processes. The control scheme, design concept and circuit realization are presented in this paper.