Integrating OFDM Into Switching Power Supplies for Visible Light Communications

Visible light communications (VLC) is a promising technology that combines the ubiquity of illumination devices with broadband communication to provide connectivity. The most recent VLC communication standards specify orthogonal frequency division multiplexing (OFDM) as the underlying modulation due to its spectral efficiency and compatibility with existing broadband modems. However, a key challenge remains in realizing VLC modulators capable of generating OFDM signal compatible with the primary illumination function, while ensuring the efficacy of the luminaires. In this paper, a novel method is proposed to integrate OFDM modulation into a switching power supply. Commutating diodes in the DC/DC converter are replaced by light-emitting diodes (LEDs) which are used for communication while the larger illumination string of LEDs is left unmodulated preserving the quality of illumination and luminaire lifetime. Biasing the switching MOSFET to its saturation region during its off states allows for the MOSFET to act as an amplifier, amplifying the OFDM communication signal and injecting it to the light-emitting commutating diode (LECD). As a result, energy efficient LED drivers capable of OFDM signal transmission are realized. Both simulation and experimental results are provided to demonstrate the feasibility of this approach, showcasing superior performance compared to existing literature in terms of component count, efficacy, illumination quality, and reliability. Notably, based on simulation results, the efficacy of our approach surpasses the bias-T approach by approximately 6.25%.