Laptop Displays – CompTIA A+ 220-801: 3.2

| December 31, 2012


The display in a laptop includes a few features not found in traditional desktop displays. In this video, you’ll learn about the most common laptop display technologies and how the laptop display can also provide additional features beyond just an output device.

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Most of our laptop displays are LCD. They are liquid crystal displays. There are small pieces of liquid crystals inside of that display that are a certain color. And when light passes through it, we see that color with our eyes.

This gives us a lot of advantages for a portable device. It’s very lightweight. And if you have a laptop or some other portable device, that’s certainly an important aspect of that. It also uses a relatively low power when you compare it to other options you might have inside of something like a laptop.

And the cost to produce these has now come way down. Very inexpensive to have a high quality, color display made of liquid crystals inside of your laptop or other portable device.

Some of the challenges with LCDs are pretty well known. One is the black levels that you can get. Because you have to have a backlight shines through the display, it’s very difficult to get really, really dark black color. So there’s a problem with getting an exact color match when you’re using something like an LCD.

That LCD backlight is also required so that we’re able to see those colors. But if there’s a problem with the backlight, then you now have to take the entire device apart and fix the backlight that’s behind it. So it becomes a little bit more difficult to replace whenever you need to get into that laptop LCD.

An emerging technology on mobile devices is OLED, the organic light emitting diode. OLED displays use chemicals that then produce light that we’re able to see, using different colors. It’s a great technology for portable devices because you don’t need a backlight. So there’s a lot of space inside these portable devices you can save, along with the power associated with it.

And OLED displays are really beautiful. They’re really crisp. They’re really clear. And the colors are fantastic.

This is also a perfect technology for small gaming systems because the refresh rates are very fast. When you have those games that have a lot of action inside of them, the OLED display works very nicely for that.

These also have a very low power draw. When you have a black color on the screen, there is so little power that’s being used. The only time you’re really ramping up the power use is when you have colors other than black that you need to see.

All of these advantages sound really good. But unfortunately, OLED is still an emerging technology as far as portable devices are concerned. So the costs are still pretty high when you compare it to LCD technology. And when the difference in the newer LCDs and the OLEDs is really not that important for most people, everyone tends to go with the lowest cost associated with them. But as the OLED technology matures, we will certainly see more portable devices using OLED displays in everything that they’re doing.

A flat panel display technology that’s been around for a long time is plasma displays. These plasma displays are so notable for the absolutely brilliant color that they can provide on the screen. And if we have a portable device, that’s something that would be nice to have.

Unfortunately, plasma technology up to this point, uses a lot of power. The LCD displays that we use today are already using about 25% to 30% of the power usage of that portable device. Adding plasma into this mix would take that number up even higher.

So a lot of engineers would love to be able to use plasma technology on their laptop. So they have to re-engineer how plasma is going to work. They need to take that power drain and really reduce the amount of power that would be used in these portable devices. And if they can manage to do that, we would be able to put some of these plasma displays in our portable devices. But up until now, that’s a technology that still is outside the scope of things like our laptop computers.

The displays on our portable devices do more than just put information on the screen for us these days. They’re also used for our wireless antennas. So if you’re connecting to an 802.11 network, there’s usually two separate antenna wires inside of your screen. Sometimes if you have Bluetooth, that Bluetooth antenna is also going to be inside of your display device.

And it makes sense that we would put it inside of our laptop screen. That’s the thing that is the highest point of this portable device. And we open the lid of our laptop, it’s there at the top. So we are going to run that antenna wire all the way up as high as we can. That way when you’re using your laptop, you’re getting the best possible wireless signal you can.

As we mentioned earlier, the LCD that’s inside of your laptop needs a backlight. It needs a light that then shines through the screen, that ultimately shows that information to your eyes. And if you have a fluorescent light that’s inside the back of your laptop screen, then it needs to have some additional power. And usually those fluorescent lights need to run in alternating current. But of course, our laptop is running in direct current. So behind that laptop screen are something called inverters that will take that DC power that’s coming into the laptop and converts it now into AC power that is used to power those fluorescent lights.

If you turn on your laptop and you’re not really seeing anything on the screen, you may want to look closely and determine is the problem with the LCD display itself or can you pick out some faint information on the screen? It may be that the backlight is no longer working because the inverter has failed. And if that’s the case, then the screen is displaying information, but because there’s no light behind it, it becomes very, very difficult to see.

So you want to be sure if you’re planning to repair this kind of problem, that you look very, very carefully. Examine the LCD display itself. Make sure that you can see information that’s there. And if that’s the case, then you can decide to perhaps replace the inverter. That way, the problem is only with the light that’s behind the display and not the LCD itself.

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Category: CompTIA A+ 220-801

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