An electronic structure comprising: a circuit board, wherein electronic devices and a transformer are disposed on the circuit board, wherein the transformer comprises a first coil, a second coil, and a magnetic body comprising a pillar with at least one portion of the pillar being disposed in a through-opening of the circuit board, wherein the first coil is wound around an upper portion of the pillar and the second coil is wound around a lower portion of the pillar for forming the transformer.