Abstract: A power device includes a mainboard and a power conversion module. The mainboard includes a first side and a third side opposite each other along a first direction, a second side and a fourth side opposite each other along a second direction, the first direction is perpendicular to the second direction. The power conversion module includes a primary-side circuit board and a secondary-side module. The secondary-side module includes a secondary-side circuit board, and the primary-side circuit board, the mainboard and the secondary-side circuit board being electrically connected, the primary-side circuit board and the secondary-side circuit board are spatially separated. The secondary-side module further includes secondary-side element and a first magnetic core element, wherein the secondary-side element and the first magnetic core element are disposed on the secondary-side circuit board along a third direction perpendicular to the first direction and the second direction.