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Transcript
SUKHNANDAN COLLEGE
MUNGELI
A PRESENTATION ON
LED & LCD
BY:
RAMAKANT CHANDRAKAR
What is LED?
 A light emitting diode (LED) is essentially a PN junction
opto-semiconductor device.
 It emits a monochromatic (single color) light when
operated in a forward biased direction.
 LEDs convert electrical energy into light energy.
How Does An
Work?
a. When sufficient voltage is applied to
the chip across the leads of the LED,
electrons can move easily in only one
direction across the junction between
the p and n regions.
 When a voltage is applied and the
current starts to flow, electrons in the
n region have sufficient energy to move
across the junction into the p region.
3
How Does A LED Work?
1.Each time an electron recombines with a
positive charge, electric potential energy is
converted into electromagnetic energy.
2.For each recombination of a negative and a
positive charge, a quantum of electromagnetic
energy is emitted in the form of a photon of
light with a frequency characteristic of the
semi-conductor
material
(usually
a
combination of the chemical elements gallium,
arsenic
and
phosphorus)..
4
Inside a Light Emitting Diode
Transparent
Plastic
Case
2. Terminal
Pins
3. Diode
1.
Driving LEDs
Two type of DRIVING LED

Analog LED Drive Circuits

Digital LED Drive Circuits
6
Analog LED Drive Circuit
7
Digital LED Drive Circuits
8
Some Types of LEDs
Bargraph
7-segment
Starburst
Dot matrix
9
Advantage of an LED
 Efficiency
 Small
is high
size
 On/Off time is less .
 Slow failure
 Lifetime
Applications of an
• Sensor Applications
• Mobile Applications
• Sign Applications
• Automative Uses
• LED Signals
• Indicators
11
Liquid-Crystal (LCD) Displays
1. What’s Liquid Crystals (LC)

intermediary substance between a liquid and solid state
of matter.
e.g. soapy water

light passes through liquid crystal changes when it is
stimulated by an electrical charge.
13
2. Introduction to Liquid Crystal Displays
A liquid-crystal display (LCD) is a flat panel display
that uses the light modulating properties of liquid
crystals.
 Liquid crystals do not emit light directly
 It consists of an array of tiny segments (called pixels)
that can be manipulated to present information
 Using polarization of lights to display objects
 Common wrist watch and pocket calculator to an
advanced VGA(video graphic array) computer screen

14
Different types of LCDs
There are Two type of LCDs available
1.Passive Matrix LCDs
2.Active Matrix LCDs
15
Active Matrix V/S Passive Matrix LCDs
Passive Matrix LCD
Active Matrix LCD

Allow high resolution

Allow very high resolution

It is usually limited to about 50
rows

It isn`t limited to about 50 rows

Each sub-pixel is individually
controlled by an isolated thinfilm transistor (TFT).

More use in Laptop & TV


Each sub-pixel is not individually
controlled by an isolated thinfilm transistor (TFT).
Less use in Laptop & TV
LCD Display Technology
Technology
 Better
Enhancements:
color through corrected CCFLs, LEDs
 Improved
 Higher
black levels (compensating films)
 Wider
contrast (pulsed backlights)
 Higher
viewing angles (compensating films)
resolution (1920x1080)
 Improved
LC twist times
Advantages

Very compact and light.

Low power consumption.

Very little heat emitted during operation, due to low power consumption.

No geometric distortion.

Is very thin compared to a CRT monitor, which allows the monitor to be
placed farther back from the user, reducing close-focusing related eyestrain.

Can be made in almost any size or shape.

No theoretical resolution limit.

Can be made to large sizes (more than 24 inches) lightly and relatively
inexpensively.
.
Applications
 Thin
Film Transistor (TFT)
 Alpha-numeric
 Back
 For
display
lighting systems
brighter displays
Comparison Between LED & LCD
LED
LCD

Power Consumption is less

Power Consumption is more

Faster response rate time

Slower response rate time

Sizes Available

Sizes Available
17inches and 70inches.
15inches to 65 inches

Color Accuracy is less


Cannot be extremely slim

Color Accuracy is more
Can be extremely slim
AND
THANK YOU FOR YOUR
PATIENCE….