An Enhanced Multi-frequency Small-signal Model for the Close-loop Design in Buck Converters

Due to the effective frequency limitation of the small-signal model derived from the average model for buck converters, the multi-frequency small-signal model was found to solve this issue by taking another dominant sideband frequency component into consideration. Based on it, this paper proposes an enhanced multi-frequency small-signal model considering two dominant sideband frequency components, which has a better prediction of the high-frequency performance. What's more, the modeling process is simplified by replacing the describing function with frequency domain analysis. And the loop gain for close-loop design derived from the new model still maintains simplicity, which guarantees the using-friendly of this new model. In addition, an important factor which influence the accuracy of this model is also shown to guide the application. Simulation and experimental results are presented as verifications.