Design and analysis of buck boost converter based LED Driver for Enhancing the Stability

Abstract

This paper develops a light emitting diode (LED) driver circuit based on buck-boost converter including parasitic resistance. The transfer function analysis of buck boost converter and whole system has been obtained by considering parasitic resistance of the component because the resistance of an LED varies with temperature, making the circuit unstable. The forward bias of the LED used was 3.0V~4.5V, and the forward current was 0.6A. Ten 3W white-light LEDs were driven in series in the proposed circuit. In an LED only 15% to 25% of electrical energy is converted into light; the rest is converted into heat, which increases its temperature. In some typical application like designing of lighting system for underground coalmines this change in resistance can cause hazardous effect. Hence, LED must be operated at constant current for constant illumination for at least 10-12 hours without failure. Therefore, a closed-loop control system has been designed in this paper to increase output voltage stability. The driver circuit is operated in continuous buck-boost mode and the results are then simulated using PSIM software. The transfer function analysis has been done by using averaging method. For, stability analysis MATLAB has been used and it has been observed that phase margin is 93.8.