Controladores led CA-CCde dupla função com VLC e interruptor único

Abstract

This document proposes a doctoral thesis that aims to contribute to the development of visible light communication (VLC) transmitters by developing dual-purpose LED drivers, powered from the AC mains with a single switch, that enables both lighting and data transmission. The proposed solutions present new approaches for low-data-rate transmitters using FSK (Frequency-shift keying) modulation. The first VLC transmitter alternative is based on power factor correction (PFC) flyback circuit operating in discontinuous conduction mode (DCM). The role of the converter is to regulate the average output current via the duty cycle value for lighting purposes and to modulate digital data by means of the first switching harmonic of the output current. Both features can be achieved simultaneously by modulating the PWM signal fed to the single-switch of the flyback converter. In order to allow for the transmission of VLC data, the converter output low-pass filter has been replaced by a 3rd order bandstop (notch) filter and an additional feedforward loop was introduced. This strategy maintains the simplicity of the original topology while granting it the functionality of transmitting VLC data with a reduced component count. Experimental results taken from a 14-W prototype supplied from a 127-V 60-Hz grid were carried out in order to verify the modulation scheme and the feasiblity of the VLC transmitter, which was able to transfer data with a bit rate of 15 kb/s over a distance of 2 m with a global efficiency of 93.3%. Following this, a performance study of the VLC system was carried out for three different types of waveform, revealing that the square wave is less susceptible to noise. The second VLC transmitter alternative employs a buck-boost flyback topology. This configuration utilizes a PFC stage operating in DCM mode to achieve a high power factor and a PC stage operating in CCM mode without an output capacitor. This setup enables a square waveform in the LED current without the need for an additional switch. Comprehensive experimental results were obtained for a 35 W prototype powered from a universal input (90 to 264-V 60 Hz), validating the operation across the entire operating range and evaluating the performance of the VLC transmitter under nominal input voltage conditions. These results demonstrate the feasibility of achieving data transmission rates of up to 248 kb/s over a distance of up to 3 m with an overall peak efficiency of 82.7%. Finally, the main contributions of the thesis are discussed and some proposals for future work are presented.