Influence of Ambient Temperature on Optical Characteristics and Power Consumption of LED Lamp for Automotive Headlamp

In this study, the authors propose a method for evaluating the influence of ambient temperature (T_a) on the optical characteristics and power consumption of a LED lamp used for the automotive headlamp, which helps the designer to figure out the acceptable range of the ambient temperature for the LED lamps to work well in the practical case. The LED lamp was fixed on the test holder and placed in a fixed position in the air circulation temperature control oven to measure the illuminance, spectrum in three different directions, and power consumption under various T_a. The experimental results indicate that T_a has little effect on the correlated color temperature (CCT), chromaticity coordinates, and angular distribution of the emitting light. In contrast, T_a has a significant effect on the lamp’s resistance, thus affecting illuminance and power consumption. When the T_a increased from 30 °C to 60 °C, the illuminance of the low beam and high beam decreased on average by 16.6% and 21.7%, respectively, while the power consumption of the low beam and high beam decreased on average by 21.4% and 22.2%, respectively. The drop in the luminous flux output indicates the probability of originally qualified automotive LED headlamps becoming unqualified in high T_a.