NICOR White Paper
What is LED Lighting?
NICOR®, Inc.
2200 Midtown Place NE
Albuquerque, NM 87113
800.821.6283
www.nicorlighting.com
NICOR LED™ is a Trademark of NICOR®
By Manoj Kumar
7/23/2012
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INTRODUCTION
LED Terminology
This paper introduces the reader to LEDs, how they work and the
advantages over traditional light sources like incandescent and
fluorescent lamps.
WHAT IS AN LED (LIGHT EMITTING DIODE)?
SSL
Solid State Lighting, term
being used for light being
emitted from a semiconductor
source rather than a gas or
filament.
A LED is a semiconductor device that emits light on certain
wavelengths. A semiconductor chip (die) mounted on a Printed
Circuit Board (PCB) with power, driver, heat sink, lens, reflector,
and diffuser, comprises a LED fixture or LED luminaire. A LED
emits both heat and light. Light is emitted in the form of particles
called photons.
LED
Light Emitting Diode, LED
produces light by the
movement of electrons inside
a semiconductor chip. LEDs are
PN junctions.
Driver
A simple electronic circuit used
to connect an LED to the main.
It converts AC to DC while
reducing the drive currents for
the LEDs.
Lumen Depreciation
Reduction in light output
(lumens) over the lifetime of
the LED.
LED Array
WHY DO I NEED A LENS, REFLECTOR AND DIFFUSER IN AN LED FIXTURE?
A LED mounted on a printed circuit board emits light in nearly
180 degrees.
Junction Temperature
Temperature at the PN
junction due to heat.
PCB
PCB stands for Printed Circuit
Board. It is a thin plate on
which chips and other
electronic components are
placed.
The OPTICAL LENS acts a collimator, transmitting light in a more
aligned direction.
A REFLECTOR increases efficiency by ensuring as much light as
possible is leaving the fixture.
White Paper
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INTRODUCTION
This paper introduces the reader to LEDs, how they work and the advantages over traditional light sources
like incandescent and fluorescent lamps.
WHAT IS AN LED (LIGHT EMITTING DIODE)?
A LED is a semiconductor device that emits light on certain wavelengths. A semiconductor chip (die)
mounted on a Printed Circuit Board (PCB) with power, driver, heat sink, lens, reflector, and diffuser,
comprises a LED fixture or LED luminaire. A LED emits both heat and light. Light is emitted in the form
of particles called photons.
WHY DO I NEED A LENS, REFLECTOR AND DIFFUSER IN AN LED
FIXTURE?
A LED mounted on a printed circuit board emits light in nearly 180
degrees.
The OPTICAL LENS acts a collimator, transmitting light in a more
aligned direction.
LED Heatsink
A REFLECTOR increases efficiency by ensuring as much light as possible is
fixture.
leaving the
A DIFFUSER spreads out or scatters light and hides individual LEDs.
A HEAT SINK provides a path for heat to travel from the LED to the exterior of the fixture where it
dissipates in the surrounding air, thus cooling the system.
WHAT IS THE LIFE TIME OF AN LED?
The Lifetime of a LED is generally considered to be the number of hours it takes to reach lumen
depreciation by 30 percent, as suggested by the Illuminating Engineering Society (IES). The human eye can
notice a difference in light output when it drops to 70 percent of the original lumen output. This metric is
indicated as L70.
White Paper
Flicker: Common Causes and How To Avoid It
3
3
INTRODUCTION
This paper introduces the reader to LEDs, how they work and the advantages over traditional light sources
like incandescent and fluorescent lamps.
WHAT IS AN LED (LIGHT EMITTING DIODE)?
A LED is a semiconductor device that emits light on certain wavelengths. A semiconductor chip (die)
mounted on a Printed Circuit Board (PCB) with power, driver, heat sink, lens, reflector, and diffuser,
comprises a LED fixture or LED luminaire. A LED emits both heat and light. Light is emitted in the form
of particles called photons.
WHY DO I NEED A LENS, REFLECTOR AND DIFFUSER IN AN LED FIXTURE?
A LED mounted on a printed circuit board emits light in nearly 180 degrees.
The OPTICAL LENS acts a collimator, transmitting light in a more aligned direction.
A REFLECTOR increases efficiency by ensuring as much light as possible is leaving the fixture.
A DIFFUSER spreads out or scatters light and hides individual LEDs.
A HEAT SINK provides a path for heat to travel from the LED to the exterior of the fixture where it
dissipates in the surrounding air, thus cooling the system.
WHAT IS THE LIFE TIME OF AN LED?
The Lifetime of a LED is generally considered to be the number of hours it takes to reach lumen
depreciation by 30 percent, as suggested by the Illuminating Engineering Society (IES). The human eye can
notice a difference in light output when it drops to 70 percent of the original lumen output. This metric is
indicated as L70.
WHICH FACTORS DETERMINE AN LED’S LIFETIME?
The lifetime of a LED product is mainly determined by the luminaire design.Factors that effect the LED
lifetime are thermal management, amount of drive current, quality of the
LED and even ambient factors such as room temperature and humidity. Of these, thermal management
is perhaps the most important factor in the life of an LED. The resin’s which encapsulate the LED’s force
most of the heat to be transferred through the back of the led array and then conducted out of the fixture
through the heat sink where heat dissipates into the surrounding air. Without proper thermal management,
the junction temperature of the LED rises, which results in color shifting, reduction in light output levels,
and a shortened LED life.
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