A Single-Inductor Multi-Output Current-Mode LED Driver With Soft-Switching

Multiple output converters are now being preferred for multi-string LED applications since they optimize on cost, size and efficiency. Additionally, using a common inductor for all the output channels reduces the hardware count and improves power density. Such single-inductor multiple-output converters further lend themselves to chip integration. LED intensity being current dependent, the present trend is to have a single-inductor, multichannel current source converter for driving multi-string LEDs. This paper proposes a zero voltage transition soft-switching of the main switching device which drives the single inductor, so as to reduce switching losses. Each output channel can be individually controlled. Based on the analysis of the governing equations during the different modes of operation, design parameters have been arrived at and simulation results confirm the analysis. Hardware implementation is done using the Spartan FPGA system and the results have been presented.