Page 179 - CITS - Electronic Mechanic - TT - 2024

ELECTRONICS MECHANIC - CITS

The construction and working process of an LCD TV involve several key components and processes that work
together to produce images on the screen. Here’s an overview
1 Liquid Crystal Display (LCD) Panel: The LCD panel is the primary component of an LCD TV. It consists of
two layers of glass with a liquid crystal solution sandwiched between them. The liquid crystals are organic
compounds that can change their molecular structure when an electric current is applied.

2 Backlighting System: Behind the LCD panel, there is a backlighting system that provides illumination to
the display. In older LCD TVs, fluorescent lamps were commonly used as the backlight source. However, in
modern LCD TVs, Light Emitting Diodes (LEDs) are the preferred choice due to their energy efficiency and
better color reproduction.

3 Color Filters: On top of the LCD panel, there are color filters arranged in red, green, and blue (RGB) sub-
pixels. These filters control the passage of light and determine the colors displayed on the screen. By varying
the intensity of the backlight and the alignment of the liquid crystals, different colors and shades can be
produced.
4 Polarizing Filters: Polarizing filters are placed on both sides of the LCD panel. These filters help control the
orientation of the light passing through the liquid crystals. The first polarizing filter polarizes the light from the
backlight source, while the second polarizing filter controls the light that reaches the viewer’s eyes.

5 Transistor Array: Each pixel on the LCD panel is controlled by a thin film transistor (TFT) array. The TFT array
acts as a switch, regulating the voltage applied to the liquid crystals in each pixel. By applying the appropriate
voltage, the liquid crystals twist and align to control the passage of light, thus forming the images on the
screen.
6 Controller Circuitry: The controller circuitry consists of integrated circuits and processors that receive input
signals from various sources, such as HDMI, VGA, or component inputs. These signals are then processed
and converted into electrical signals that control the operation of the LCD panel and other components of the
TV.
Working Process
1 The backlighting system emits white light.

2 The white light passes through the first polarizing filter and enters the liquid crystal layer.
3 The liquid crystals twist and align according to the electrical signals received from the TFT array, modulating
the passage of light.

4 The modulated light passes through the color filters, which determine the colors displayed on the screen.
5 Finally, the polarized light passes through the second polarizing filter and reaches the viewer’s eyes, forming
the images and colors on the screen.

Advantages and Disadvantages of LCD TV
LCD TVs offer several advantages and disadvantages compared to other types of televisions like CRT or plasma.
Here’s a breakdown

Advantages of LCD TV
1 Slim Profile: LCD TVs are much slimmer and lighter compared to older CRT televisions, making them easier
to mount on walls or place in various locations within a room.

2 Energy Efficiency: LCD TVs consume less power than CRT TVs, making them more energy-efficient and
environmentally friendly. This results in lower electricity bills and reduced carbon footprint.
3 High Resolution: LCD TVs typically offer high-resolution displays, providing sharp and clear images with
vibrant colors and excellent detail, especially in HD and UHD (4K) models.
4 No Screen Burn-In: Unlike plasma TVs, LCD TVs are not susceptible to screen burn-in, where static images
can become permanently imprinted on the screen over time.
5 Wide Viewing Angles: Modern LCD TVs have improved viewing angles compared to earlier models, ensuring
that viewers can enjoy consistent picture quality from various positions in the room.

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CITS : E & H - Electronics Mechanic - Lesson 100 - 107