Unlike conventional lamps that fail abruptly, LEDs depreciate slowly over time. The life of an LED is defined as when its lumen output depreciates to 70%.
What is LED Lighting?
LED stands for Light Emitting Diode. It emits light when current passes through it.
What is junction temperature?
It is the temperature of the PN junction in the LED chip.
What are the challenges with LED Lighting?
LEDs are very sensitive to temperature and also produce a lot of heat during operation. This heat should be removed from the system to maintain the junction temperature within prescribed limits. LEDs are point sources, so are prone to cause glare if the optics is not properly designed.
What is the role of heat sink?
Heat sink is required to dissipated heat generated by LEDs during operation. Since ambient temperature in India varies from – 5 0C to + 55 0C so the heat sink design should ensure effective thermal management under all circumstances. It should be made of high grade aluminum & should have no pores (like in gravity die cast heat sinks) providing resistance to heat flow. Garnet uses aluminum pressure die cast or extrusion heat sinks.
What is the physical significance of 50,000 hrs life?
4 hr daily operation: 34 yrs
8 hr daily operation: 17 yrs
12 hr daily operation: 11 yrs
24 hr daily operation: 5 yrs
What are basic Lighting Definitions?
Lumen (lm): It is a unit of luminous flux and a measure of the total amount of visible light emitted by a source.
Efficacy (lm/W): It is a measure of how efficiently a lighting source produces visible light per unit of input wattage. LEDs have high efficacy >150 lm/W compared to GLS 10 lm/W or CFL 60 lm/W.
Lux (lm/m²): It is the unit of illuminance and measures the luminous flux per unit area. Each application has its standard lux requirements. The task-oriented areas like kitchens or sewing will require high lux values compared to non-task areas like corridors or lobbies.
Correlated Colour Temperature (K): It is a method of describing the colour characteristics of light, usually either warm (yellowish), neutral (off-white) or cool (white), and measuring it in degrees of Kelvin (°K).
Colour Rendering Index (CRI): It is the ability of a light source to produce natural colours. For example, an object seen in sunlight will show the natural colours (high CRI), whereas it will show different colour if seen under blue or green light (low CRI).
Beam Angle: It indicates the spread of light from the light source. A narrow beam gives concentrated light, which is better for accent lighting. A wide beam gives a more general, softer light suitable for ambience lighting applications.
How is the life of LEDs compared to conventional lamps?
GLS: 1,000 hr
Halogen: 2,000 hr
CFL: 5,000 hr
FTL: 6,000 hr
LED: 50,000 hr
What are the benefits of LED Lighting?
LEDs have numerous benefits over conventional lighting technologies –
a. Saves up to 50% energy over CFLs b. Have long life of 50,000 hrs c. Do not emit UV and IR radiations d. Do not contain mercury e. Can produce millions of colour options
What happens if the junction temperature increases?
An increase in junction temperature may drastically reduce LED performance, like:
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