\documentclass{standalone}

\usepackage{tikz,pgfplots}
\usepackage{siunitx}
\usepackage[siunitx,european]{circuitikz}
\usepackage{mathrsfs}
\usetikzlibrary{arrows}
\usepackage{amsbsy}
\usetikzlibrary{fadings}
\usetikzlibrary{patterns}
\usetikzlibrary{automata,positioning}
\usepackage{mwe,subcaption,tikz}
\tikzset{boximg/.style={remember picture,red,thick,draw,inner sep=0pt,outer sep=0pt}}
\pgfplotsset{compat=1.11}
\begin{document}
\definecolor{mygreen}{rgb}{0,0.78,0}
\begin{tikzpicture}

\draw[<->, thick] (0,3.25) |- (5,0) node[right]{$t$};
\draw[blue, thick] (0,0.02) -- (1.02,0.02) -- (1.02,3) -- (2.52,3) -- (2.52,0.02) -- (3.52,0.02) -- (3.52,3) -- (5,3) node[right]{$u_T$};
\draw[blue, thick, dashed] (0,2) -- (5,2) node[right]{$U_{in}$};
\draw[mygreen, thick] (0,1.25) -- (0.98,1.75) -- (0.98,0.02) -- (2.48,0.02) -- (2.48,1.25) -- (3.48,1.75) -- (3.48,0.02) -- (4.75,0.02) node[above]{$i_T$};
\draw[mygreen, thick, dashed] (0,1.5) -- (5,1.5) node[right]{$I_{Ton,avg}$};
\draw[<->] (1.77,2) -- (1.77,3) node[midway, fill=white, scale=0.99]{$N\cdot U_{out}$};
\draw[<->] (1.5,1.25) node[below]{$\Delta I_m$} -- (1.5,1.75);
\draw[dashed] (1.75,1.25) -- (0,1.25)
(1.75,1.75) -- (0.75,1.75);
\draw (1,0.1) -- (1,-0.1) node[below]{$\frac{D}{f_{sw}}$}
(2.5,0.1) -- (2.5,-0.1) node[below]{$\frac{1}{f_{sw}}$};

\end{tikzpicture}
\end{document}