A Two-Stage Multiple-Output Automotive LED Driver Architecture

This paper is focused on a two-stage LED driver architecture operating from an automotive battery input voltage and delivering independently regulated output currents to multiple LED strings. The system consists of a non-inverting buck-boost front end, which handles wide battery voltage range, followed by high-frequency immittance-network based LCL-T resonant converters, which operate as current sources over wide output voltage ranges. The two-stage architecture allows for system efficiency optimization by taking advantage of the passthrough mode of operation of the non-inverting buck-boost stage and the buck and boost regulation capabilities of the immittance network resonant converter stages. Experimental results are provided for a prototype consisting of a 400 kHz front-end stage and 2 MHz LCL-T stages delivering independently regulated 0.55 A currents to two LED strings with N = 1 —12 LEDs. The measured system efficiency is greater than 85% over wide input (8-18 V) and output (3-36 V) voltage ranges, with a peak efficiency of 93% when the buck-boost stage is in the pass-through mode at the nominal battery voltage.