Topology and Control Innovation for Auxiliary Power Supply in Dimmable LED Drivers

In this paper, a cost-effective architecture based on Flyback topology is proposed for both constant current (CC) output for LED drive and constant voltage (CV) output for auxiliary (AUX) supply. A novel nonlinear ramp-based control scheme is proposed to decouple the main CC power train from the CV AUX supply and avoid LED output flickering. Small signal modeling is presented to highlight the advantages of this control scheme over conventional peak current mode control. This scheme has been implemented successfully for a 40-W dimmable LED driver with a 12-V 3-W AUX supply.