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 $\times 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 °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%.

Keywords

• Adaptive front-lighting systems
• smart headlamp
• active-matrix
• over temperature protection
• pulse width modulation