Design, Analysis and Implementation of New Durable Streetlighting LED Driver Topology

Abstract

Light Emitting Diode (LED) fixtures are widely used in streetlighting owing to their durability, high luminous efficacy, and low power consumption. LED drivers which are ac/dc converters are required as an interface between the LEDs and the grid voltage. There are certain requirements mandated by standards for the safe operation and requirements relevant to the performance of streetlighting LED drivers. Most important ones include a Power Factor Correction (PFC) circuit that is essential for every high power streetlighting LED driver to achieve high Power Factor (PF), and low Total Harmonic Distortion (THD), and output light flickers of a streetlighting fixture that must be maintained under a certain limit to create a healthy lighting environment. This thesis presents a high PF, flicker-free LED driver consisting of a novel buck-boost typed PFC circuit integrated with an asymmetric half-bridge LLC resonant converter. The proposed buck-boost PFC unit operates in Discontinuous Conduction Mode (DCM), and achieves almost unity PF and acceptable THD. The proposed topology limits the dc bus voltage to nearly the peak value of input sinusoidal voltage reducing the voltage stress of MOSFETs. The control system of the LED driver is designed such that the output light flickers are mitigated without using any electrolytic capacitors in the circuit. Furthermore, the proposed LED driver achieves high efficiency throughout a wide operating range owing to the Zero Voltage Switching (ZVS) obtained in LLC switches, and optimal magnetic designs. Simulation and experimental results based on a 200 W laboratory prototype are presented to verify the effectiveness of the design and control systems. The laboratory prototype provides the maximum efficiency of 94.6%, power factor greater than 0.98 at full-load, and below 15% output current ripples.