Design of a contactless battery charger for cellular phone

In this paper, the design of a contactless charger for a 3.3 W lithium-ion battery of a cellular phone is presented. In this charger, the primary core of the transformer is in the charger unit and the secondary core is in the telephone. The gap (3 mm) between them is the thickness of the two plastic cases. The transformer core design for the maximum coupling coefficient and the maximum magnetizing inductance with the size constraint on the secondary side is presented. A half-bridge series resonant converter is used to compensate the leakage inductance and to achieve ZVS operation. Voltage gain, current gain analysis, and design procedure are presented. For the battery charging control, an infrared LED is used and its performance is verified from the hardware experiments