Printed circuit board planar current transformer for GaN active diode

In this paper, a Printed Circuit Board (PCB) Planar Current Transformer is proposed for GaN synchronous rectifier. This type of current driven synchronous rectifier is also known as the “Active Diode”. Planar current transformer provides minimal thickness. Primary and secondary windings are fabricated on either side of the PCB. The shape of the windings and their relative positions are studied for the best coupling and current sensing. U shape primary winding and rectangular spiral secondary winding are found to produce a maximum coupling factor. A GaN Active Diode with the proposed PCB current transformer is built. It is adopted in a 500 KHz, 12 V to 5 V, 10 A output buck converter which demonstrates the advantages of the proposed Active Diode. A very thin Active Diode module is presented. An additional 5 % efficiency improvement is achieved compared with Schottky diode.