State-Trajectory Control With Single-Cycle Response for Point-of-Load Converters

A popular variable-frequency control used for point-of-load (POL) converter application is the constant on-time (COT) control. COT control is able to improve light-load efficiency and reduce the amount of output capacitors with high-bandwidth designs, but the transient response of COT control is limited by the fixed on-time nature of the control. In this paper, a state-trajectory-based control with single-cycle transient response is proposed for POL converters. With the proposed control, the converter will follow the natural state trajectory of the converter for the duration of the detected load step-up transient, which can ensure a very fast transient response. Experimental results are presented to not only demonstrate the proposed idea but also the control's ability to further reduce the amount of output capacitors and save board footprint.