A single-inductor, multiple-channel current-balancing LED driver for display backlight applications

A single-inductor boost LED driver that can distribute equal DC currents to multiple channels of LEDs is presented. To ensure uniform brightness in display backlight units, the previous approaches used current regulation elements serially inserted in individual LED channels, which incur power losses. Instead, the proposed LED driver adopts a single-inductor multiple-output (SIMO) boost converter topology, which keeps the channel currents equal in an open-loop fashion by connecting the current-delivering inductor to each channel for an equal period of time, in a time-division multiplexing manner. Furthermore, the sequence of conduction is continuously permutated in order to reduce possible systematic imbalances among the currents. A prototype LED driver demonstrates the peak power efficiency of 93.0% excluding the FPGA controller power and maximum current balance error of 2.04% while delivering 12.4-W to three channels of high-brightness white LEDs.