Which of the following are used on a laptop to provide power for the fluorescent backlight?

HomeFAQ and Articles Screen backlight type. How to find which one is in your laptop.

CCFL screens are now obsolete. If you have a post 2011 laptop more than likely it is equipped with a LED screen. We do not stock any CCFL screens any more.

If you still curious how things used to be in those prehistoric times carry on reading:

Three ways to find out what type of backlight is in the screen of your laptop.

1. Take the screen out of the laptop and see the back of it: if there is a cable and a connector for the inverter, you have a CCFL screen, if the connector is not present, then the screen is LED.
2. Refer to the owners manual of the laptop.
3. Contact the manufacturer of the laptop or find the information on it's website.

LCD panels are divided into two types according to the backlight type CCFL and LED.
These two types of screens have completely different connectors and power supplies. They are not compatible.

CCFL (Cold Cathode Fluorescent Light - High Intensity Discharge Lamps)

- This type of lighting is used in older laptops. Usually it comes with one lamp, more ralely - two, this type of backlight needs an inverter (high voltage transformer) to power it's lamp(s)
CCFL single lamp has only one power plug, and this type of CCFL screens are more widespread:

CCFL with two lamps has two power connectors, and it is much more rare than single bulb:

LED (Light Emitting Diodes - LED Backlight)

- This type of lighting has been widely used in the early 2010s. It consists of Light Emitting Diodes and is considered more energy efficient. Such screens do not need an inverter, that's why they only have a video connector.

For step by step video instructions on How to replace the screen in a laptop click here.

LCD screens can suffer from various problems, but several symptoms of display problems are quite limited:

• No picture at all, the screen does not show signs of life (sometimes the power light does not come on).
• Screen switches itself off after a certain period of time (short times to a few seconds after start-up).
• The screen shows a very dark, faded picture and a significantly low level of brightness.
• A completely white screen, and the screen doesn’t show any picture at all.
• The screen has a line or a colored vertical lines which aren’t part of the displayed picture.
• The monitor shuts down after a while
• HDMI port doesn’t work, the monitor shows “No signal”
• Takes long time for the monitor to turn on

In order to understand what could cause such problems and how to solve them, one needs to understand the mechanics of LCD (Liquid Crystal Display which is screen-based liquid crystals).

How does the LCD screen work?

LCD screens rely on several technologies in order to display an image:

1. Polarized glass –  Polarized glass will pass light waves in a certain angle. Therefore more light is blocked. If you put two glasses with the same polarization one after the other, the light will pass through both. If, however, the first glass will have a polarization that is perpendicular to that of the second glass, the light will not go through at all.

2. Liquid crystal molecules – the uniqueness of these molecules is that they are able to pass light through, and are affected by electrical current which changes the way the light passes through the molecule.

3. Transparent conductive materials – electric current is run in LCD screens and should reach every pixel, for this purpose transparent conductors are used. This makes it possible to avoid seeing it on the screen and causing interference with the picture. An example of a transparent conductive material (which is typically used in LCD screens) is indium – the oxide of tin.

The LCD screen is made up of two glasses that are connected to each other, and a backlight located behind. The glasses are made of liquid crystal molecules, which are designed to be influenced by electric current. They are distorted by 90 degrees (e.g., light enters from one side, leaving a polarized glass at 90 degrees on the other side). If there is no electricity transferred into the molecule, the light that is coming from one side of the screen will not pass through a polarizing glass, otherwise it will be rotated 90 degrees in the molecule and then pass through the second polarizing glass.

When an electric current passes through the molecule at different volumes, it is undergoing varying degrees of deformation and the light is being twisted at an angle between 0 and 90 degrees. This way various shades of gray being delivered. To receive a colored image, arrayed sub-pixels of red, blue and green, similar to the CRT screens need to be added (so, each pixel consists essentially of three sub-pixels that are able to display any combination of red, blue and green, and actually show each color).

What causes LCD screen problems?

Now that it is clearer how an LCD screen works, you will be able to review the problems caused by abnormalities in various parts.

1. Power supply
The power supply is responsible for supplying electric current to every component of an LCD screen. Therefore, any abnormalities will usually cause varies problems in the screen. In addition, if not handled in time may cause the screen to get irreparable. The power supply is a component that can be repaired or replaced in our lab.

2. Backlight
A backlight provides light that passes through the LCD crystals. A backlight uses fluorescent bulbs or LEDs, once it is compromised in one way or another nothing can be displayed on the screen or will displayed faded image. If the backlight will lose its vividness it will cause the screen to display a dark and faded image (because the maximum brightness level decreased significantly). Our lab can replace old bulbs or defective new bulbs and return the LCD screen to life.

3. Inverter
Inverter is a device that provides current to the backlight module. An inverter provides a very high voltage to fluorescent bulbs and much lesser voltage for LEDs. The Inverter sees that all bulbs or LEDs are stable and working, therefore, any irregularity leads immediately to the invertor’s protection module activated and shutdowns backlight. A faulty inverter cannot supply the required current and voltage over time. It is usually responsible for problems connected only with backlight. The screen brightness will be affected, if the inverter cannot supply the current that is needed to run the backlight at full power. The inverter is a component that can be repaired or replaced in our lab.

4. Motherboard of LCD screen
The motherboard is the main component, includes processor that is responsible for decoding the signal which comes from a computer’s graphics card. It also controls an inverter, power supply and the LCD screen. Malfunctioning motherboard can result in all kind of problems with the monitor.

5. Array of liquid crystals
Liquid crystals can be damaged in any way in the LCD screen itself. In this case, the result will usually be dead pixels (pixels that display consistently the same color, regardless of the picture).
There are other problems with LCD screens that are caused by faulty components on the LCD graphics card.

As you can see, most of the problems with LCD screens are caused by faulty components which can be repaired or replaced. This is much cheaper than buying a new LCD screen. Also it is the most economical way.

If you have any questions or are interested in consulting a computer technician please contact us or call 054-225-7705

Which type of screen uses a fluorescent lamp as the backlight?

How does a laptop screen backlight work?

What type of laptop display backlight requires an inverter?

What are the types of laptop screen backlight?