A magnetic assembly includes a magnetic core and a winding. The magnetic core comprises an upper cover, a lower cover and at least one core column provided between the upper cover and the lower cover, the core column presents a prismatic shape and has at least two lateral surfaces, the lateral surfaces intersect with each other to form at least two longitudinal ridges, and the longitudinal ridge extends along the longitudinal direction of the core column. The winding, winding around the core column, a first semi-conductive component is provided between the core column and the winding at the position corresponding to the longitudinal ridge.