On the Use of the Intrinsic Ripple of a Buck Converter for Visible Light Communication in LED Drivers

In this paper, we present the analysis of a novel technique to implement visible light communication (VLC) into light emitting diode (LED) drivers with minimum hardware requirements and efficacy degradation. It uses a synchronous buck converter as a circuit for a dual-purpose LED driver for illumination and VLC. The role of the converter is to regulate the average current via the duty cycle value for lighting purposes and to modulate digital data through the phase of its ripple waveform. In this technique, the phase of the pulsewidth modulator acts as an independent variable to modulate the ripple waveform for a binary phase-shift keying modulation and does not affect lighting regulation. Thus, the transmission of wireless digital data uses the remaining ac content present in the waveform of the ripple. By detecting the phase of the ripple, a VLC receiver can decode the data sent by the transmitter. Finally, our experimental results show that the efficacy of the LED is not affected by the value of the ripple when operating outside its nonlinear region, along with minimum global efficacy degradation when compared with a standard synchronous buck converter with the same parameters and no VLC capabilities.