begin{document}
begin{tikzpicture}[edge from parent fork down,auto]
 tikzset{
 treenode/.style={align=center,draw},
 root/.style={treenode, inner sep= 10pt, text width = 5cm, font=large},
 1/.style={treenode, inner sep= 7pt, text width = 3cm},
 2/.style={treenode, inner sep= 5pt, text width = 1.5cm},
 level/.style={level distance=1.5cm},
 level 1/.style = {sibling distance=7cm},
 level 2/.style = {sibling distance=3cm}
 }


 node[root](tree){Wurzel}
 child{node[1]{Ast1}
  child{node[2]{Zweig1}}
  child{node[2]{Zweig2}}
 }
 child{node[1]{Ast2}
 child{node[2]{Zweig3}}
 child{node[2]{Zweig4}}
 };
 path[auto=false]
 (tree-1.east) -- node{X} (tree-2.west)
 (tree-1-1.east) -- node{/} (tree-1-2.west)
 (tree-2-1.south east)-- node[below=.25cm]{Text} (tree-2-2.south west)
 ;
 end{tikzpicture}

HEADER
  _______|________
   |              |
isolierte      non isolated
   |              |
flyback          buck
active           boost