\begin{tikzpicture}[>=latex]
\matrix[]
{
      \pgftransformscale{.7}
      \fill[gray!30] (0,0) -- (0,0.0625) -- (0.05,0);
      \fill[gray!30] (4,0) -- (0.925,0) -- (1,0.0625) -- (4.0,0.0625);
      \fill[gray!60] (0.05,0) -- (0.4,-0.4375) -- (0.925,0);
      \draw (0,0.0625) -- (0.4,-0.4375) -- (1,0.0625) -- (4,0.0625);
      % horizontal axis
      \draw[->] (-0.2,0) -- (0.5+4,0) node[right] {$t$};
      \draw (0.4,0) -- (0.4,0.1) node[above] {$T_1$};
      \draw (1,0) -- (1,-0.1) node[below] {$T_2$};
      \draw (4.0,0) -- (4.0,-0.1) node[below] {$T_s$};
      % vertical axis
      \draw[->] (0,-1.5) -- (0,1.5) node[above] {$i_{C_{in}}(t)$};
      \draw (0,0.0625) -- (-0.1,0.0625) node[left] {$I_{in}$};
      \draw (0,-0.4375) -- (-0.1,-0.4375) node[left] {$i_2$};
      \node at (2.0,-2.0) {$P_A + P_B = 0.25$};
&
      \pgftransformscale{.7}
      \fill[gray!30] (0,0) -- (0,0.49) -- (0.392,0);
      \fill[gray!30] (4,0) -- (2.212,0) -- (2.8,0.49) -- (4.0,0.49);
      \fill[gray!60] (0.392,0) -- (1.12,-0.91) -- (2.212,0);
      \draw (0,0.49) -- (1.12,-0.91) -- (2.8,0.49) -- (4,0.49);
      % horizontal axis
      \draw[->] (-0.2,0) -- (0.5+4,0) node[right] {$t$};
      \draw (1.12,0) -- (1.12,0.1) node[above] {$T_1$};
      \draw (2.8,0) -- (2.8,-0.1) node[below] {$T_2$};
      \draw (4.0,0) -- (4.0,-0.1) node[below] {$T_s$};
      % vertical axis
      \draw[->] (0,-1.5) -- (0,1.5) node[above] {$i_{C_{in}}(t)$};
      \draw (0,0.49) -- (-0.1,0.49) node[left] {$I_{in}$};
      \draw (0,-0.91) -- (-0.1,-0.91) node[left] {$i_2$};
      \node at (2.0,-2.0) {$P_A + P_B = 0.7$};
&
      \pgftransformscale{.7}
      \fill[gray!30] (0,0) -- (0,1) -- (0.8,0);
      \fill[gray!30] (4,0) -- (2.8,0) -- (4,1);
      \fill[gray!60] (0.8,0) -- (1.6,-1) -- (2.8,0);
      \draw (0,1) -- (1.6,-1) -- (4,1);
      % horizontal axis
      \draw[->] (-0.2,0) -- (0.5+4,0) node[right] {$t$};
      \draw (1.6,0.0) -- (1.6,0.1) node[above] {$T_1$};
      \draw (4.0,0) -- (4.0,-0.1) node[below] {$T_s$};
      % vertical axis
      \draw[->] (0,-1.5) -- (0,1.5) node[above] {$i_{C_{in}}(t)$};
      \draw (0,1) -- (-0.1,1) node[left] {$i_1$};
      \draw (0,-1) -- (-0.1,-1) node[left] {$i_2$};
      \node at (2.0,-2.0) {$P_A + P_B = 1$};
\\
};
\end{tikzpicture}
