LED Lighting Basics

LED array LED lighting Light Emitting Diode

A Light Emitting Diode (LED) is a solid state lighting device that converts electrical energy directly into light. LEDs have revolutionized lighting today and are increasingly used for a wide range of applications in residential, commercial and
industrial lighting for their energy savings, flexibility and durability. Below are some LED lighting common terms.

Anode: The positive terminal of a diode.

Bin: To sort or classify LEDs into groups according to specifications such as
their luminous intensity, voltage or color appearance.

Chip: A term used for the board or “light engine” to which the LEDs are
applied. The chip or “light engine” is a circuitry board for the LED.

Colour Corrected: Refers to a lamp, such as an LED, with a special phosphor or coating to give it a color rendering profile similar to natural daylight.

Die: Is the chip or the light emitting semiconductor.

Diode: A two-terminal semiconductor device having a p-n (positive negative)
junction which allows energy to travel in one direction.

Driver: A self-contained power supply that has outputs which match the electrical characteristics of the lamp. It is similar to a ballast and is used to power  illumination sources.

Flicker: The strobing of some luminaires that cannot be visually detected  because of the frequency of its output voltage.

Heat Sink: A heat sink is an environment or object that absorbs and dissipates
heat from another object. The design of an LED retrofit lamp’s heat
sink is an integral factor in the overall performance of the lamp.

LED Array: A predetermined pattern of a number of LEDS mounted on a printed
circuit board (PCB) or other surface which produces light when power is provided.

Lens: A lens is an optical device that refracts light, converging or diverging the
beam.

L70: Is a measure of the Lumen depreciation in an LED.

LM79: An IES approved method describing procedures and precautions in
performing reproducible measurements of LEDs including total flux, electrical power, efficacy (lpw) and chromaticity. This is applicable to LED products incorporating control electronics and heat sinks (LED luminaires and integrated LED sources).

LM80: An IES approved method for measuring lumen depreciation of solidstate
(LED) light sources, array and modules. This does not apply to luminaires and does not define or provide methods for estimation of life.

Power Factor (PF): Measurement of the relationship between the AC source voltage and current. Power factors can range from 0 to 1.0, with 1.0 being ideal.
Power factor is sometimes expressed as a percent. “High” power factor usually means a rating of 0.9 or greater.

Solid-State Lighting (SSL): Lighting that uses LEDs to emit light from a solid object -a semiconductor- rather than from vacuums or gas tubes used in
incandescent and fluorescent lighting. Solid-State Lighting does not contain moving parts that can break or shatter, potentially contaminating the environment.

TM-21: IESNA TM-21-11 provides the method for determining when the “useful lifetime” of an LED is reached, a point when the light emitted from an LED depreciates to a level where it is no longer considered adequate for a specific application through the use of extrapolated data from LM80 testing. Lumen maintenance of LED products and LED packages can vary by manufacturer. TM-21 ensures consistent lumen maintenance extrapolation methods for all LED manufacturers. TM-21 extrapolations are ‘best-case’ system lifetime estimates, and assume that no other failure mechanisms influence the life of the LED
luminaire. 


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