Ripple-based visible light communication technique for switched LED drivers

Visible-Light Communication (VLC) is the transmission of data using the visible-light spectrum. It uses the rapid response of light devices, such as Light Emitting Diodes (LEDs), to modulate the emitted light in order to transmit information. In this work, we present a novel and simpler modulation technique for VLC. It uses the Pulse Width Modulator (PWM) of a DC/DC converter, which acts as a power source for an LED load. Hence, we apply a split-phase modulation by changing the PWM carrier's phase at each bit transition, causing a transition of the output current ripple. By detecting the ripple, the receiver can decode the data sent by the light source. Additionally, average duty cycle value is not affected by transmission. Transmission data rate is a multiple of the switching frequency. Finally, experimental results using a synchronous buck converter as a driver for a 22.6 W LED load operating with a current ripple of 30% showed successful transmission and detection of a bit stream sequence in a Light-Of-Sight (LOS) configuration for over a distance of 1.5 m. The converter's switching frequency is of 100 kHz, giving a data-rate of 50 kbps.