Fourier-Series Models of DC-DC Converters

The paper presents new models of DC-DC converters. The sub-circuit formed by the voltage source, switching transistor, and diode, is replaced by an independent square-pulse current source, while the rest of the circuit remains unchanged. Using Fourier series representation of current-pulse square wave, the current source is describe as a sum of sinusoidal currents, thus the system is considered linear. The system´s state- space representations in the time domain and s-domain are derived. Comparison of the buck converter state-space representation of both models is performed. Numerical validation of the buck converter is presented. The Fourier series models developed in the paper offer the benefits of large-signal models and small-signal models combined, without sacrificing accuracy, and is well suited for transient analysis of power systems incorporating DC-DC converters.