Impact of LED Current Waveforms on FSK-Based VLC Performance and Design of a Flyback Driver for Square-Wave Modulation

This paper analyzes the performance of Visible Light Communication (VLC) systems when different LED current waveforms are applied, aiming to guide the design of switched-mode converters using Frequency Shift Keying (FSK) modulation schemes. Theoretical calculations and experimental tests were carried out using sinusoidal, triangular, and square current waveforms. Results indicate that the square waveform offers superior noise immunity, enabling transmission over distances up to three times longer than the other types, while maintaining a satisfactory Bit Error Rate (BER). In addition, this work presents a method for designing an LED driver capable of producing square-shaped current signals, based on a flyback converter operating in Continuous Conduction Mode (CCM). This topology enables single-switch control of both the average current and the data modulation. A laboratory prototype rated at 35-W and powered by a 300-V dc supply with a 13.7-V ripple was built and tested, demonstrating reliable data transmission over distances of up to 3 meters, achieving satisfactory BER and reaching data rates of 234 kb/s.