LM-80 Test Report (Lumen Depreciation of LED Chip)
The North American IES standard LM80 determines a test method by which a batch of LEDs are tested at a specified drive current and ambient temperature. At intervals during the test luminous flux, and CCT are measured. At least 2 ambient temperatures are used in the test: 55°C, and 85°C. The LEDs are operated at these temperatures and at a specific drive current for a period of 1000hrs, then the LEDs are taken from the oven, allowed to cool to 25°C ambient and their light output characteristics are measured. The LEDs are then placed back in the oven and the process repeated for a minimum of 6000hrs (approximately nine months).
Once the LM80 test has concluded, the measurements are used to determine a depreciation curve for the luminous flux at each temperature. The data is extrapolated using the method described in the North American Technical Memorandum TM21 to determine the "Lumen Maintenance Life Projection (Lp)". The end point of the extrapolation is typically 70% of the initial light output.
LM-80 refers to a method for measuring the lumen depreciation of solid-state light sources, such as LED packages, modules and arrays. Typically, LED component manufacturers each report lumen maintenance data using their own methodology making it vary hard to compare “like for like”.
It was developed by the Illuminating Engineering Society of North America (IESNA), to allow people the ability to evaluate and compare the lumen maintenance of LED components from different companies.
It is typically a 6000hr test (can be 10,000hrs) that shows depreciation and chromaticity shift over the period at particular operating temperatures 55 degrees, 85 degrees and a third manufacturer defined temperature.