An Auxiliary-Parallel-Inductor-Based Sequence Switching Control to Improve the Load Transient Response of Buck Converters

In this paper, a sequence switching control (SSC) scheme based on an auxiliary parallel inductor is proposed to improve the transient performance of buck converters. The proposed SSC scheme introduces a small controlled inductor in parallel with the output inductor, so as to increase the inductor-current slew rate when it is activated during a load transient. Furthermore, an "n + 1" sequence switching strategy is proposed to control the auxiliary parallel inductor. The proposed scheme divides the transient event into n + 1 periods. In the former n periods, the same small output voltage deviations are designed, while in the last period, a smaller deviation is done for a smooth transition from the transient to the steady state. The switching sequence is derived applying the capacitor-charge balance principle for each of n + 1 periods. For a given buck converter in the experiment, the settling time and the output voltage deviation of the proposed SSC scheme enhance more than 50% and 67%, respectively, over those of the time-optimal control for a 3-A load step.