A printed circuit board transformer comprises at least one primary winding and one secondary winding, each in the form of at least one layer of turns inside or at the surface of a printed circuit board. The transformer is designed for a step-up/down-operation. Each of the two layers (10, 11) has an elongated...http://www.google.com.tw/patents/US7978041?utm_source=gb-gplus-share專利 US7978041 - Transformer
