LED products are invented to consume lesser energy, last longer, and be more efficient than traditional lamps and CFL; however little people know what really determines the lifetime of a LED product, and how the lifetime of a LED is measured or tested.
All electric light sources experience a gradual process of lumen depreciation, which refers to a decrease in the amount of light they emit overtime. Incandescent filaments evaporate over time, and this typically results in 10-15% depreciation compared to initial lumen output over the 1,000 hour life of an incandescent lamp. Compact fluorescent lamps (CFLs) generally lose no more than 20% of initial lumens over their 15,000 hour life. The faster the lumen depreciates means the faster the light output quality depreciates, which in result, determines the usable lifetime of the bulb.
The primary cause of LED lumen depreciation is heat generated at the LED junction, which is why good thermal engineering is very essential to a LED product. Continuous exposure to high temperatures without proper ventilation will spoil LED bulb components, which directly affects the product’s lifespan.For example,electrolytic capacitor’s lifetime decreases by a factor of 2 for every +10°C increase in temperature. If an electrolytic capacitor is designed to perform 8,000 hours at a temperature of 105°C, when poor product design keeps the heat inside the bulb body and increases the temperature to 115°C, this component can only last for 4,000 hours instead.
Another key factor to LED product’s lifetime is its chips. It is easy to understand: with other factors remain the same, the better the chips the longer the lifespan of the bulb. Wellmax’s Sunrise series LED bulbs use high quality chips that passed the LM-80 test, which is required prior to applying Energy Star or INMETRO certification. The LM-80 test measures the lumen maintenance of chips at a high temperature. Our chips can maintain over 95% lumen (depreciate less than 5%) at 105°C after 6000 hours continuous testing. This guarantees the quality and lifespan of our LED bulbs.
Temperature of the bulb and quality of LED chips are two main factors that determine the overall quality and lifetime of LEDs. In next week’s newsletter, we will introduce to you in detail how exactly the lifetime of LEDs are tested.
(Source: U.S. Department of Energy, BuildingTechnologies Program, “Lifetime of White LEDs”, http://apps1.eere.energy.gov/)