A Two-Stage Automotive LED Driver with Multiple Outputs

This article presents a two-stage automotive LED driver architecture delivering independently regulated output currents to multiple LED strings. The system consists of a multiphase noninverting buck-boost front-end stage, which allows for a 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 buck-boost + resonant (BB+resonant) architecture takes advantage of the buck and boost capability of both stages, and the flexibility in setting the intermediate bus voltage to minimize losses. Advantages of the BB+resonant architecture include the use of lower voltage rated devices and soft switching in the resonant stage, leading to reduced losses and size. Experimental results are provided for a prototype consisting of a 250-kHz two-phase front-end stage and 2-MHz LCL-T resonant stages delivering independently regulated 1 A currents to four LED strings with N = 1$-$ 18 LEDs. The measured system efficiency is greater than 88% over wide input (8$-$18 V) and output (3-50 V) voltage ranges, with a peak efficiency of 93%.