An Improved Dimmable LED Driving Scheme with Low Flicker Metrics for Low Voltage Application

Abstract

In the field of dimming of high brightness LED, variable duty ratio pulse-width-modulation (PWM) operated LED dimmable drivers are commonly used which cause high flicker metrics resulting visual discomfort and health risks of the viewer as pointed in recently reported IEEE Std. 1789-2015. In IEEE Std. 1789-2015, a low flicker metrics such as flicker index and modulation depth are recommended to avoid those health hazards. Such flicker metrics are to be calculated from modulating LED current and have to be sufficiently low and also modulation depth should lie within a prescribed operating region as recommended in IEEE Std. 1789-2015. In this paper a variable-frequency constant duty ratio PWM operated novel driving scheme has been proposed for DC-DC wide range dimmable LED driver which performs dimming with a low flicker metrics. The reported driving scheme does not require any electrolytic capacitor in the driver unit and hence low life span of electrolytic capacitor does not deteriorate life span of LED driver unit. Both simulation and experimentation have been carried out and reported in this paper with adequate responses. Also comparative analyses of flicker metrics of the proposed driving scheme with existing conventional PWM operated dimmable LED drivers have been reported.