A 2.8-MHz 96.1%-Peak-Efficiency 1.4-μs-Settling-Time Fully Soft-Switched LED Driver With 0.08–1 Dimming Range

Abstract

Present day LED drivers demand both high power efficiency and wide dimming range. However, these two parameters are often a tradeoff, where a wide dimming range requires a high switching frequency, hence the ensuing switching losses. In this paper, we present an LED driver that features both high power efficiency and wide dimming range by means of fully soft switching that substantially eliminates the switching losses, i.e., the switching losses are negligible. We achieve the said fully soft switching by our proposed hysteretic soft-switching controller (HSSC) and the proposed circuits—voltage detector, current sensor, and level shifter. The HSSC enables the fully soft switching, including zero-voltage switching and zero-current switching, by means of turning on / off power switches when their voltage/current is zero. The proposed voltage detector and current sensor, featuring low power, monitor the voltage and current of the power switches. The proposed level shifter, featuring ultra-fast speed, serves to quickly transmit the monitored signal from the said voltage detector and current sensor to the HSSC. The prototype LED driver, realized in a 130-nm BCDLite process, features 6–18 V input voltage range, output current of 0.5–1.3 A, drives 1–3 series-connected LEDs, 12-W maximum output power, 2.8-MHz maximum switching frequency, 96.1% peak power efficiency, 1.4-μs settling time, and 0.08–1 dimming range at 20-kHz dimming frequency. When benchmarked against state-of-the-art LED drivers, our design simultaneously features the widest dimming range, shortest settling time, and requires the smallest inductor. The measurements and benchmark depict the decoupling of the said tradeoff.