The Design of Two-Step-Down Aging Test for LED Lamps Under Temperature Stress
In this paper, the step-down aging test for light-emitting diode (LED) lamps is designed according to the stopping rule of the IESTM-28 standard and experimental data. The step-down aging experiment is under the temperature stresses of 90 °C, 80 °C, 70 °C, and 60 °C, from which the temperatures for two-step-down aging test are selected. A Nelson model is used to calculate the equivalent time from one temperature to another, and a two-stage method is adopted to establish the reliability model of LED lamps under accelerated temperature. Then, the lifetime at the ambient temperature of 25 °C is deduced by the use of Arrhenius model. It is shown that the temperatures of 90 °C and 80 °C for two-step-down aging test are the best choice, with standard deviation of reliability and standard deviation of relative lifetime less than 11% and 20%, respectively. The accelerated aging time is <;1200 h, which meets the requirement of quick lifetime prediction of LED lamps.