Patent ID: 8890519

Claim:
An apparatus comprising a printed circuit board, said printed circuit board comprising a stack, along a vertical direction, of several metallization layers mechanically separated from one another by electrically insulating layers, at least one first coil and one second coil series-connected to each other, said first and second coils being wound respectively around first and second vertical winding axes, each of said coils comprising turns formed by conductive tracks made in said metallization layers and electrically connected to one another by through-pads passing through at least one of said electrically insulating layers, wherein joining of said conductive tracks and said through-pads forms a conductive line that extends continuously from one end of said first coil to an opposite end of said second coil, wherein said at least one first coil and one second coil comprises a common first conductive track, made in a first metallization layer, wound around said first vertical winding axis and wound around said second vertical winding axis, and a common second conductive track, made in a second metallization layer, wound around said first vertical winding axis and wound around said second vertical winding axis, and a first pad passing through at least one of said insulating layers to electrically connect said common first conductive track and said common second conductive track to each other so that, when said first and second conductive tracks are powered, current always turns in the same sense around said first vertical winding axis and always in the same sense or in an opposite sense around said second vertical winding axis.