Current equalization in parallel LEDs using flyback converter

Advisors: Donald Zinger.Committee members: Michael Haji-Sheikh; Martin Kocanda.With increasing demand in energy, Light Emitting Diodes (LEDs) are rapidly finding new applications. Parallel combination of LEDs is better than existing solutions for high intensity load requirement than the series combination, as it does not put constriction on number of LEDs to be used. But there are certain discrepancies in using LEDs in parallel combination. Forward voltage change and input voltage drift pose problem in current sharing in parallel branches. This thesis presents a new, cost effective and simple method to design current equalizing circuit that will allow uniform current sharing in parallel LEDs.;The proposed circuit uses magnetically coupled inductors to balance current in parallel branches of unequal loads. The circuit uses a flyback converter to achieve this. High frequency switching used in the circuit helps to minimize visible flicker. The duty cycle of switching MOSFET and inductors of transformer can be used to balance the current in branches along with maintaining the brightness of LEDs. The circuit is tested for larger imbalance in load. Previous work done to reduce current mismatch in loads is discussed. A comparative study is between these methods and the proposed method is presented.M.S. (Master of Science