US Patent 7804388 Transformer

A transformer is provided. The transformer comprises a coil frame, an input coil and an output coil. The input coil and the output coil are both disposed on the coil frame and interlaced with each other. A second voltage outputted by the output coil is induced by a first voltage inputted into the input coil. The output coil comprises at least one metal strip to enhance the output power. The coil frame is formed with a plurality of coil openings with chamfered angles or rounded angles, so that the bended angle formed by the input coil at the location where the input coil passes each of the coil openings is substantially less than 15 degrees.