US Patent 7446640 Leakage transformer

A leakage transformer includes a primary winding; a secondary winding wound at a part on an extension of a winding part of the primary winding separately from the primary winding and having a coil sectional area smaller than that of the primary winding; a center core part composed of two core members and linearly extending through the primary winding and the secondary winding; and a peripheral core part formed by extending part of the two core members at the center core part and forming a magnetic path on the outer side of the primary winding and the secondary winding.