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noob question regarding lcd inverters

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#1 andras


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Posted 04 May 2014 - 05:12 PM

If laptops run on AC power, what is the need for an inverter that changes current from dc to ac when the laptop is already running on ac? I cant get my head around this sorry. can someone explain this to me please? where is the inverter getting the DC from to convert to AC to power the backlight? 

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#2 OldPhil



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Posted 04 May 2014 - 08:09 PM

Lap Tops runs on DC, You have answered your own question.

Edited by OldPhil, 04 May 2014 - 08:10 PM.

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#3 zingo156


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Posted 05 May 2014 - 08:59 AM

The current from the wall is AC ~120 volts, the computer runs on DC ~12-20 volts this is what the power adapter does, it turns AC to DC and lowers the voltage to whatever the computer uses.


The inverter drives the back light, the back light (fluorescent bulbs) require high voltage power somewhere around 1000 volts, the laptop power adapter only outputs somewhere between 12 volts and 20 volts (most newer laptops are 19-19.5 volts). The inverter in laptops increase the voltage so the fluorescent bulbs will work correctly.


Newer laptops do not require a inverter because they use LED back lights, the LED back lights do not require high voltage current.

Edited by zingo156, 05 May 2014 - 01:35 PM.

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#4 andras

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Posted 05 May 2014 - 01:03 PM

thanks for your replies folks. Doesn't take much to confuse me :) 

#5 dc3


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Posted 05 May 2014 - 01:49 PM

There are currently two types of laptop displays, LCD (Liquid Crystal Diode) and LED (Light Emitting Diode).


The LCD display requires high voltages to power the Cold Cathode Fluorescent tube, because of this an inverter is needed to boost the voltage.


The LED display requires much less voltage, as a result it doesn't require an inverter.  The back light for these is produced by the use of LEDs.


A LED display produces a brighter screen and is reputed to have a clearer image.

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