8. Backlight

To be possible to see picture on LCD display, at back of LCD glass must be ambient white light and that we call "backlight" .

In LCD screens are two types of backlight, doing the same job, made light allowing us to see picture on LCD :

 - CCFL lamp backlight

 - LED strings/chains backlight   

LED backlight subject is more complicated than CCFL, so it is separated to this subpage a. LED backlight  

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Here is information about CCFL lamp backlight and his driver named "inverter".

Work with lamps is easy, as basically any inverter can drive any CCFL lamp, so we can exchange inverters for the CCFL lamps and always it should work good.

To have easy work with inverters, I recommend to use universal inverters available in China, 

they works always well.

You can use bigger one or smaller, possible to hide in laptop bracket.

Those universal inverters have one more advantage, that they work even if CCFL lamp is a bit "tired" (no keeps parameters), in such case, normal inverter will turn lamp off, but universal will still lights up.    

Small universal inverter works in wide range of supply Voltage 5V-28V (in practice better use voltage more than 9V), is available in this store with good prices

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Some ask, if possible to use laptop's inverter, 

answer is yes and not  

Normally, in laptop along with LCD screen in bracket are also CCFL inverter.

So why to not use this inverter again with our LCD screen ?

Well, theoretically it is possible as in general all inverters works in the same principles.

It need power, GND , BL(on/off signal) and ADJ(dimming) , unfortunate the problem is usually in details.

Inverters use various chips and electrical parameters of inverters, vary from brands and vendors.

Some inverters need power 5V only, some 12V, some 18V-20V. Some need two voltages.

BL signal range for some is 0V-1.8V, for some 0-3V, for some 0-5V etc.

Dimmig also between 0-5V or 2V-4V or 0-1.9V, some need 3bit digital dimming, etc. All depends on particular inverter from particular laptop.

Some are working well with power 12-18V and have BL as 0-5V - so will work for us without problems, but we must know about this parameters for sure. 

In generally, they are a bit problematic.

So, that mean is not possible to use them ? no, is possible to use them but we need more readings and more work, what is time consuming.

If do not like reading, measuring and soldering etc. - simply buy universal CCFL inverter, they are not expensive.           

Otherwise, below are samples, how to use the original ones.

More easy to reuse are CCFL inverters from monitors, they usually works well without problems using 12V,GND,BL and ADJ  signals.

Normally, only BL signal is enough for good work.

Also is possible, to use monitor's universal inverters for 2 or 4 CCFL lamps

2 lamp inverter you can buy  IN THIS SHOP

  4 lamp inverter is available IN THIS SHOP  or THERE    

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First example, it is inverter from HP (do not know model) , normally this inverter will not work at all with universal board, but after reading of OZ960 chip datasheet, there was information about two voltages, 12V for lamp's transformer and additional 5V supply for chip, BL range was normal 0-3.3V.

OK let check it with his original display, 15'' display 1024x768. 

First testing with universal inverter to check display works well, than connection of 12V, 5V, GND and BL for original inverter - it works

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Another sample is bracket with 1280x800 display.

It have inverter made on MP1011 chip, and works as good as universal inverter - so we need only 12V, GND and BL for proper work

Let check it - it works :)                                                                         we can close bracket

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  in progress