Design, implementation and measurement of board-to-board wireless power transfer (WPT) for low voltage applications

In this paper, we present measurement results of board-to-board wireless power transfer (WPT) for low voltage applications using resonant coupling. WPT system consists of source coil, receiver coil, rectifier and load on printed circuit board (PCB). Among them, spiral coil is expressed as a simple equivalent circuit, of which the components are calculated using its physical configurations. The measurement result in frequency-domain shows a good correlation with simulation result using the simple equivalent circuit. In addition, CMOS full bridge rectifier with low turn-on voltage is designed and fabricated to be mounted on PCB. In this system, it is observed that turn-on voltage of the rectifier is very small and DC level at the load is sufficient to be adapted to low voltage applications. Consequently, coil-to-coil voltage transfer ratio (VTR) and DC level at the load of board-to-board WPT are achieved to be 0.50 and 1.32V, respectively. Power transfer efficiency of 30% is calculated using circuit simulation.