High-speed LED driver for visible light communications with drawing-out of remaining carrier

The visible light communications that communicates by modulating the light of illumination, which is the existing infrastructure, attracts attention. So as to improve the speed, to increase the bandwidth, and to miniaturize hardware of this communication system, improvement in the transmission speed by a single LED for lighting is important. The transmission speed of an LED is greatly restricted by the carrier that remains in junction capacity. Therefore, the transmission speed can be increased by drawing out the remaining carrier. We proposed and applied the carrier drawing-out circuit to the driver circuit that drives a blue LED. An optical measurement shows that the fall time decreases from 56 to 10 ns (decreases to one fifth), and the horizontal eye opening ratio has been improved from 29% to 61% (increases to 213%) for 50 Mb/s PRBS.