Temperature-Aware Adaptive Control for Automotive Front-Lighting System

Abstract

Adaptive front-lighting systems (AFSs) have been widely adopted to automotive industries for providing higher driver's safety. As their light sources, multi-string light-emitting diodes (LED) arrays have been widely adopted because of their simpler driver controls. Recently, micro-structured AFSs (mu AFSs) with a micro-LED (mu LED) array are highly demanded for their controllability of individual LEDs. However, the integration of a mu LED array and its high-power active-matrix driver are not available on the market. Moreover, a high-power driver causes not only a significant variation in driving current, but also a higher power density requiring over-temperature protection (OTP). In this paper, the average current through each mu LED is adaptively controlled with pulse width modulation (PWM) in conjunction with an additional PWM control for temperature calibration. Experimental results with a 16 x 16 mu LED array placed on top of the proposed driver show that a 5-bit PWM signal controls the average current through each mu LED cell up to 11 mA. The maximum current error of 4.11% at 100 degrees C is reduced to 0.23%. When OTP is enabled, the amount of average pixel current reduction depends on the given temperature. The maximum power efficiency of the proposed mu AFSs driver is as high as 92.3%.