Suppressing start-up time variation versus load current — Adaptive soft-start in boost LED drivers

This paper proposes an adaptive soft-start technique which offers both dynamic overshoot protection at start-up and maximum current regulation during steady state. The circuit is included in a boost converter IC Controller manufactured in a 50V, 0.5μm CMOS technology and tested via simulations and measurements. A comparative study is performed regarding converter´s operation with and without the proposed block. Results emphasize the proposed solution´s ability to suppress overshoots and reduce start-up time. Moreover, the measured start-up time is quasi-constant for a fixed number of LEDs, regardless of LED current.