US Patent 7295091 Leakage transformer

This is a small-sized transformer that is made easily. Two bobbins around which a secondary coil is wound insert into bobbin protrusions from the opening surface side of the first core whereby the two bobbins are positioned in a row. A coiling protrusion around which to wrap a primary coil is formed in the aforementioned first core. Part of the primary coil coils around the coil protrusion and the remainder is positioned and coiled in a groove of the aforementioned first core provided in the outer circumference of the two bobbins. A second core is positioned in a countering position to the opening surface of the aforementioned first core so as to cover the aforementioned three protrusions.