A transformer structure is disclosed. The transformer comprises a primary winding coil, plural secondary winding coils, a first winding portion, plural second winding portions, plural partition plates, a channel, and a magnetic core assembly. The first winding portion is used for winding the primary winding coil thereon, and the plural second winding portions are used for winding the secondary winding coils thereon and disposed at two sides of the first winding portion. The plural partition plates are disposed between the first winding portion and the second winding portions, respectively, and each the partition plate has a slot. The channel penetrates the first winding portion, the second winding portions and the partition plates. The magnetic core assembly comprises an I-shaped magnetic core and a U-shaped magnetic core. The I-shaped magnetic core is received in the channel and the U-shaped magnetic core has plural protrusions inserted into the slots of the partition plates. Thereby, a leakage inductance of the transformer is adjusted by a distance between the protrusions of the U-shaped magnetic core and the I-shaped magnetic core received in the channel.
A transformer is disclosed to include two bobbin, each bobbin having a primary side and a secondary side respectively holding a primary winding and a secondary winding, two first ferrite cores respectively inserted through the bobbins, two second ferrite cores arranged at two sides relative to the bobbins and abutted against each other, each second ferrite core having a middle protruding portion respectively inserted into the bobbins and to form with the first ferrite cores two independent magnetic loops. The secondary side of each bobbin has winding spaces for the winding of the wire for the secondary winding, partition flanges, vacant spaces defined between each two adjacent partition flanges, and top bridging notches and bottom bridging notches respectively formed on the partition flanges in such a manner that each vacant space has one side in communication with one top bridging notch and an opposite side in communication with one bottom bridging notch for guiding the wire of the secondary winding from one winding space to another through the vacant space without causing a potential difference.
