Investigation Into the Use of Single Inductor for Driving Multiple Series-Connected LED Channels

An investigation into the use of single inductor for driving N series-connected LED channels is presented. Each channel has a parallel-connected switch for controlling the LED channel current, as well as charging the inductor. Compared with the conventional structure having all LED channels connected in parallel and (N + 1) switches, the proposed structure has the merits of 1) requiring N switches, 2) allowing all channels to be driven concurrently in every switching cycle, and 3) being insensitive to the duration of the transition switching from one channel to another. Detailed mathematical analysis on the topological operations will be discussed. The proposed concept will be demonstrated on a two-channel structure. A prototype with two 7 W LED modules has been built and evaluated. A control mechanism that can regulate the output luminous flux and correlated color temperature without sensing the inductor current and channel currents will be discussed. Experimental results are favorably compared with theoretical predictions.