A Qi-compatible Wireless Charging Pocket for Smartphone

This paper presents a Qi-compatible wireless charging pocket for the smartphone. The wireless charging pocket is constructed to provide wireless charging in both directions so that it can be charged regardless of the direction in which a smartphone is inserted. This charging pocket consists of two transmit-coils placed on both sides of the pocket and two inverters capable of selecting coil to provide dual-way wireless charging. Each transmitting coil is designed with a focus on the Quality Factor(Q) in order to extend the transmission distance of the Q wireless charger to more than 10mm. Each transmitting coil is made of three layers of spiral coil in order to secure the Q value of more than 350 and the size of the coil that can be built into the pocket. The pocket detecting the insertion direction of the smartphone and only one inverter is selected by the detecting result. One MCU is used to perform these operations and power control functions using communication with the receiver. The communication scheme of the pocket is load modulation scheme that is used in "Qi" standard. The measurement results show that the DC/DC efficiency of the pocket are approximately 75% at 6mm transmission distance and 65% at 10mm transmission distance.