LED biasing scheme with thermal compensation for automotive industry applications

Abstract

This work introduces a novel scheme for driving light-emitting diodes (LEDs) with thermal compensation. The primary objective of the system is to address the issue of emitted light intensity drift caused by temperature variations, with a particular focus on the automotive industry. The developed technique proposes an alternative approach to the traditional thermal approach, which primarily focuses on heat dissipation. In contrast, the presented strategy utilizes a temperature-dependent element, such as a thermistor, to generate a reference current that increases with temperature. The generated current is then amplified by a commercial integrated driver and employed to bias the LEDs. Consequently, the reduction in the emitted light intensity resulting from an increase in the internal temperature of the LED is counterbalanced by an elevation in the bias current. The luminous flux model developed for the proposed system predicts the attainment of stable light intensity across a wide temperature range. The proposed strategy has been applied to three commercial LEDs commonly employed in automotive signal lighting to produce red, yellow, and white light. Experimental results confirm a significant reduction in the thermal dependence of the luminous flux, with reduction factor of temperature dependence ranging between 3.7 and 14.2 for the least and most temperature-sensitive LED models analyzed, respectively.

Keywords

• Automotive lighting
• Thermal compensation
• Integrated driver
• LED
• Thermistor