Eye Strain from LED Backlighting in MacBook Pro (2008)

Re:Eye Strain from LED Backlighting in MacBook Pro (2008) by Zak on Saturday January 06, 2018 @06:43PM (#16088148)

That would be a solution, however flicker-free dimming for LEDs is not difficult. Linear regulator chips are cheap, but inefficient. Switch-mode power supplies cost a little more. Both are mature technologies any electrical engineer should be familiar with.

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Re:Eye Strain from LED Backlighting in MacBook Pro (2008) by amelius on Saturday January 06, 2018 @07:01PM (#16088222)

Now that you make me think a little deeper about it, it seems simple indeed. The exponential V/I curve of the LED makes I unstable for a given value of V, so all you need to do is have a feedback loop that controls I.

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Re:Eye Strain from LED Backlighting in MacBook Pro (2008) by monochromatic on Saturday January 06, 2018 @09:15PM (#16088697)

LED light output isn’t linear in power input though. PWM allows you to drive the LED in its most efficient regime no matter how much brightness you want.

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Re:Eye Strain from LED Backlighting in MacBook Pro (2008) by Zak on Saturday January 06, 2018 @09:47PM (#16088811)

Efficiency tends to decrease with current. It is rarely more efficient to run higher current and PWM than to simply run lower current.

It is, however often easier in terms of circuit design.

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Re:Eye Strain from LED Backlighting in MacBook Pro (2008) by monochromatic on Saturday January 06, 2018 @09:58PM (#16088849)

That’s interesting, I thought there was an optimal range. Do you have a link with more info?

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Re:Eye Strain from LED Backlighting in MacBook Pro (2008) by Zak on Sunday January 07, 2018 @12:02AM (#16089290)

Well, I can offer an example. This is a test of an LED using a bench power supply. In this test, efficiency drops every time current is increased, without fail.

http://budgetlightforum.com/node/51693

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