Lifetime isoflux control of LED based light sources

Light output performance of power LEDs is sensitive to the junction temperature and also changes with the elapsed lifetime of the device. A smart control to achieve constant light output of LED based products would be advantageous in many applications such as street-lighting, resulting e.g. in considerable power savings when forward current is reduced when ambient temperatures are lower. Also, continuous compensation of lumen depreciation during product lifetime would improve visual comfort. Both could be made while the aging phenomena of the device are slowing down. This paper introduces a new theory for LED lumen maintenance calculation and a case study with real life data is carried out to demonstrate the feasibility of the proposed method.