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


As the Internet of Things (IoT) continues to proliferate, connected and smart solutions are influencing more and more areas of our lives, as well as lighting sector. From system point of view, the additional smart features will require separate power and voltage domains from LED load, therefore, integrating an auxiliary (AUX) power supply into LED drivers is an ideal option to facilitate LED luminaire system design and reduce system cost and complexity. 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 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 40W dimmable LED driver with a 12V 3W AUX supply.