Basic circuit theoretic considerations of LED driving: Voltage-source versus current-source driving

Light-emitting-diodes (LEDs) are solid-state devices with specific v-i characteristics. In this paper we study the basic requirement of the driving circuits and discuss the proper approach to driving LEDs from the circuit theoretic viewpoint. We compare voltage source driving and current source driving, and discuss their relative advantages and constraints. We specifically introduce the use of duality principle in developing new current-source drivers which are mostly unknown but are theoretically more versatile compared to their conventional voltage-source counterparts. Although the study exploits very basic circuit theory, it is not always borne in mind or known by practitioners the impact of the choice of circuit topologies on the current and voltage ripples, range of duty cycle variation, sensitivity, and efficiency of LED drivers. This paper presents a systematic and comparative exposition of the circuit theory of driving LEDs, with experimental evidences supporting the major conclusions. Finally, we illustrate how these results can readily lead to an effective LED driver design.