Bi-directional wireless charging between portable devices

In order to support for empty battery of portable devices with very important and urgent situations, a bi-directional wireless charging between portable devices is tested under WPC Qi specifications. The bi-directional charging is simply achieved by adding the switching elements across the rectifier diodes. As an experimental result of a prototype, system efficiencies of about 70% are obtained at an output power of 2.5W with 2mm air gap and 0~8mm lateral transition conditions.