Keywords: SMPS, switched–mode power supply, QBC, quadratic buck converters, PWM, pulse width modulation, SMC, sliding mode control, current control, flickering reduction, LED lamps, LED lamp drivers, average current mode control, ACM, modelling, transfer function derivation, controller tuning, Bode plots, simulation
An efficient sliding–mode current controller with reduced flickering for quadratic buck converter used as LED lamp driver
This paper presents mathematical analysis, design and simulation of a quadratic buck converter used as LED lamp driver, and the performance of the converter is compared with two different control strategies. The objective is to provide tight regulation of the LED current that can operate over a wide range of DC input voltages. The first control strategy is the non–linear Sliding–Mode (SM) current controller, and its design aspects include choice of sliding surface, deriving existing and stability conditions, control parameter selection and their analysis. This paper also throws light on Average Current–Mode (ACM) controller. The operation, modelling, designing and transfer function derivation for the inner current and outer voltage loops of the quadratic buck converter are presented. The tuning of controllers for the ACM controller is done using Bode plots, for achieving desired phase and gain margins. The simulation is done using PSIM software and the results are presented.