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# Why do LCD backlights draw 600mA @5V?

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#### DaKandEKid

##### New Member
I have a two 4x20 LCD's.

One has a EL backlight and the other has an LED backlight.

The LED LCD draws 375mA @ 4.2V = 1.575 Watts

This seems like a lot to me. Considering a regular led is about 20mA @ 1.5V = .03 Watts

That implies that their is either 1.575/.03 = 52.5 LEDs in the Backlight or there is some horrible inefficiency in some type of voltage step up or down.

Additionally, Is there any other display technlogy for viewing text in a potentially dark room with much lower power consumption?

You are calculating it wrong.
They use a resistor to drive the leds with 5V. This means the led will consume 20mA... at 5V!

375mA / 20mA are about 20 Leds. Sounds about right to me

Yes, i have also measured same value, it is right.

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