Using spectral analysis to determine the equivalent circuit of the output filter of DC-DC converters at their operating frequency

The aim of this paper is to present an on-line technique which can be used to determine the equivalent circuit of the storage elements of DC-DC converters at their operating frequency. This technique can be used not only for the determination of both inductor and capacitor equivalent circuits, but also as a fault diagnostic technique, in order to evaluate the state condition of these components. The proposed technique uses the spectral analysis in order to obtain the relation between inductor current and voltage, and between inductor current and output voltage ripple. From these relationships, it is possible to determine the equivalent circuit of the inductor and capacitors at the operating frequency of the converter. In this paper, several experimental and simulated results are presented in order to demonstrate the accuracy of the proposed method.