Controle robusto aplicado a driver de leds: otimização do filtro capacitivo e aumento da vida útil

Abstract

This work proposes two applications of robust control in LED drivers, aiming to improve efficiency and lifespan of these systems. The first proposal focuses on reducing the capacitive filter through the H∞ optimization technique. In LED driver devices, the use of high-capacitance capacitors is common, but this can result in high failure rates, compromising system reliability. The second proposal aims to extend the lifespan of the driver through robust control in the face of electrolytic capacitor degradation over time. The chosen driver for these proposals is a buck-boost flyback converter, designed for high power factor and compliance with standards, operating in a universal voltage range of 90 to 264 V and 75W maximum power. Control is implemented with robust state feedback, using gains determined by LMIs, ensuring stability at different dynamic operating points. Both proposals are based on active control, which minimizes the transfer of bus ripples to the output, while maintaining minimum energy quality requirements for efficient driver operation. The H∞ optimization is employed to minimize disturbances, implemented by LMIs. However, the active control strategy faces limitations due to input current distortion. These limitations are overcome with restrictions on controller gain calculation, ensuring desired output ripple and harmonic content of the input current according to standards. Additionally, a limitation on the proportional parameter of the controller is implemented to avoid amplification of unwanted noise. As a result of the application of these methodologies, a significant reduction of approximately 70% in the driver’s capacitive filter was observed in the first proposal. In the second proposal, there was a significant increase of 4100 h in the system’s lifespan. In both approaches, minimum energy quality requirements and output current ripple were maintained.