A Generic High-Frequency Model for the Nonlinearities in Buck Converters

To investigate the high-frequency behaviors for the switching converters, the modeling and analysis should include the influences from the sideband components, which are generated by the converter's nonlinearities. With a buck converter, two nonlinearities are identified in this paper: the pulse-width modulator and the switches. Based on the harmonic-balance approach, the multifrequency model is proposed to address these nonlinearities and to predict the high-frequency performances. With the derived model, different modulation schemes are compared based on their influence on the sideband effect and the control bandwidth limitations. The possible benefit from the double-edge modulation and its limitations are clarified. In addition, the audio-susceptibility is studied considering the nonlinearity of the switches. With the combination of the two nonlinearities, a generic high-frequency model is achieved. Simulation and experimental results are presented to verify the achievements of the proposed models.