DC/DC converters exhibit subharmonics and chaos when the switching action is governed by feedback control. Since the use of converters is increasing in Industries for various applications, deeper analysis of the appearance and the nature of bifurcation is essential to stabilize its output onto a desired periodic solution. Time frequency representation is helpful in studying the fine structures of frequency patterns such as sub harmonics and ultra harmonics of chaotic dynamics. This paper analyzes the changing frequency patterns during bifurcation processes of the nonlinear DC-DC Buck converter using Wigner-Ville distribution method as pattern recognition method. This information leads to a better understanding of the system that may allow us to design a stable, chaotic free converter and could be used as a diagnostic for detecting different nonlinear dynamic responses.