Design and Implementation of High Power LED Lighting System for Health Care Applications
Authors: Gnanavadivel J. , Kumar N.S. , Christa S.T.J. , Yogalakshmi P. 
Published: February 2018

Background:

A conventional front-end rectifier causes line current distortion and reduces the power factor, which result in lowering power quality for Light Emitting Diode (LED) drive system. Hence, this paper projects the design, simulation and comparison of novel PI tuned by the fuzzy logic controller with the conventional PI controller for modified SEPIC rectifier to produce the required load voltage along with supply-side unity power factor and less distorted supply current with limited harmonic content for LED lighting in healthcare applications. A prototype of 100W, 48V LED driver was developed for testing the performance of the controller.

Methods:

This paper presents the modified SEPIC LED driver with PI integrated fuzzy and classical PI for controlling voltage. For controlling source current, classical PI is chosen. Both are equipped with the modified SEPIC rectifier. Both conventional PI control and novel fuzzy tuned performances were compared.

Results:

The proposed control topology operated modified SEPIC rectifier was analyzed and the corresponding power factor and THD were measured. The operational evaluation of the proposed LED driver using fuzzy tuned-PI/PI controller combinations for different output power is provided in Table 2. Sustained regulated DC voltage of 48V was achieved even when the load resistance varied within a specific range. Power factor of 0.9995, which is close to unity, was also achieved. The relative analysis was made with conventional PI and trendy PI integrated FLC controller which is provided in Table 3. The usage of PI integrated fuzzy logic controller minimized the peak overshoot to be around 1.3% and rise time of 0.5s which are lower when compared to the conventional PI controller. With reference to Fig. (8a), the source current THD of the conventional PI controller was observed to be around 7.39%. Having PI integrated FLC, THD was further reduced and for rated load, it was found to be 1.39%. The power factor of the conventional PI controller is around 0.9974. PI integrated fuzzy logic controller improved the power factor to 0.9995 with fuzzy tuned PI controller in action as shown in Fig. (8b). A prototype of 100W, 48V LED driver was developed for testing the performance of the controller. A power quality analyser was employed for measuring power factor and THD, shown in Fig. (10a). 3.633% of harmonic distortions at the source current and 0.9980% of input power factor was achieved for rated load power. 4.510% of supply current THD with 0.9931% input power factor was achieved for low load power.

Conclusion:

This manuscript suggests a modified single switch SEPIC LED driver for 48V output operated healthcare equipment. Simulation study of this driver shows the better performance. In order to analyze the performance, a comparative study was conducted by using the classical PI and the novel PI integrated fuzzy controller. Satisfactory results regarding enhanced quality of power, regulated load voltage, quick rise time and settling time were achieved. The source current THD has been reduced to around 1.39% which is less than 5% as per the IEEE-516 prescribed standard and the power factor has been improved to 0.9995 by implementing the fuzzy tuned PI controller. The above results favor the suggested modified SEPIC LED driver for practical healthcare applications.