Model-based validation and development of LED-systems: MValEnt

摘要

Durability of LEDs is usually specified to 10,000 hours though numerous LED products feature a lesser operation life. This might be caused by faulty constructions or improper physical environments and operating conditions. Since such failure cannot be accepted for cost intensive applications in automotive, medical or illuminating engineering simulation based prediction of LEDs durability is a promising design approach. Main causes of degradation are manufacturing and operation temperatures or temperature gradients, respectively. These result in an increased diffusion, accelerated chemical reactions and induced material stresses. In a consequence, chemical, physical and mechanical properties of parts are altered. To investigate conditions of LED operation, LEDs degradation and conditions of failure a test environment considering electrical and thermal loads as well as optical emission has been designed. Furthermore, the LED test environment has been modelled within the software application MatLAB/Simulink to simulate and predict the durability of complex LED-systems. Test environment, computer-aided simulation and a test design using design of experiments are combined to a design tool named MValEnt. This supports validation and design of complex LED-systems for varied conditions of operations and component characteristics. Integrated data interfaces provide an iterative product development. Load measurements reveal different failure mechanisms due to characteristics of operating current, ambient temperature and pulse-width modulation (pwm) as well as operation interruptions. Electrical and thermal coupling of LED circuits results in additional loads and thus degradation. With increasing power mechanisms of LEDs degradation are comparable to those found in power electronics.