Keywords: Light Emitting Diodes, LC resonant converter, PWM diming, zero voltage switching (ZVS), Centre tapped transformer.
Introduction
Globally, one fifth of electrical energy goes on lighting. Hence the drive for efficient, reliable lighting systems. In virtue of their superior longevity, compactness, excellent light efficacy per watt, eco-friendly nature, and color rendering, light emitting diodes (LEDs) are replacing conventional light sources in residential, streetlights, automotive and decorative lighting applications \cite{schratz2018,raju2017,phankong2018,Veeramallu_2021,veeramallu2018}.
Since the forward current of LED alters the illumination level of the light bulb, it needs to be regulated precisely. LEDs can be powered with either linear voltage regulators (LVR) or switched mode regulators (SMPS). Nevertheless, SMPS are more commonly used power supplies owing to compactness and high efficiency. In literature, several types of converter configurations such as buck, boost and buck-boost converters are proposed, however when these converters used for the for LED lighting systems resulted in a trade-off between size of reactive component and efficiency \cite{n2019a,n2019}. Therefore, there is a need for an efficient LED driver circuit that can perform the same task with more efficiency and durability by implementation of latest converter topologies \cite{campa2010,Park_2009,singh2012,Ramanjaneya_Reddy_2017b}.
High brightness LEDs are currently used by manufacturing firms to design lamp units. In order to amplify light intensity, multiple numbers of LEDs are stacked together in series and parallel combination as per the load requirement. The intensity of light and chromaticity straight away depend on the forward current passing through the LED; therefore, it is desirable to drive LED load with constant current \cite{wendt2017,Ramanjaneya_Reddy_U_2016,udumula2015,Gacio_2009,Narasimharaju_2018,Narasimharaju_2014,narasimharaju2017,ballapu2020}. The idea is to use two sources, one to supply threshold voltage directly, the other source being the full-bridge LC series resonant converter, which regulates the LED current. It results in improved efficiency and high reliability \cite{Hwu_2009,Saikia_2016}. Fig. \ref{815650} (a) and fig. \ref{815650}(b) illustrate the LED equivalent model and concept of the proposed work, respectively.