Drive current for led 0 to 100%

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1. Need to drive a single white led, part no: 2ES103CW06000001 , datasheet: http://www.edison-opto.com/en/pr...

Datasheet says it has Vf=3.4V & If=700mA, Peak pulse current: 1A

Intensity needs to be varied from 0 to 100%.

 

2. Want to know, suppose I want to glow led at 100%, should I give maxium 3.4V/700mA  or I can increase voltage or current further for high intensity? If yes, how to calcualte maximum recommended values for safe operation

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The voltage is determined by the led and varies with temperature. Therefore you regulate the current to determine the brightness. 700mA is the specified maximum forward current for your device. You can increase the current and get more brightness, but this may affect device reliability. As such, you don't calculate it - the datasheet gives you the values. The datasheet also has a derating table for current vs temperature. Make sure you stay within the requirements.

 

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 can increase voltage or current further for high intensity?

 As mentioned by Kartman, 700 mA is the Max in spec, steady state current.

 

You can pulse it at 1 A, but that isn't a steady state value.

 

If you need more light, then use two LEDs, or pick an LED with a higher output.

 

Make sure you read the data sheet / app notes on the recommended PCB footprint and heat sinking if you are going to run it at 700 mA continuously.

 

If you use a series resistor for current limiting, then make sure it has the correct power rating, or better yet use an LED driver chip that is designed for the purpose.

 

JC

 

Edit: typo

Last Edited: Sun. Jun 2, 2019 - 11:32 AM
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d

Doing magic with a USD 7 Logic Analyser: https://www.avrfreaks.net/comment/2421756#comment-2421756

Bunch of old projects with AVR's: http://www.hoevendesign.com

Last Edited: Mon. Jun 24, 2019 - 08:59 AM
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how to calcualte maximum recommended values for safe operation

It depends on mounting, since heat will destroy.

How bright of a light do you need?  That's the first question.

You supply & monitor the current.  The voltage is secondary, just have enough available as needed.

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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What do you try to make ? 

 

It's all in the temperature of the diode, if you can keep it cold, you can get more light.

 

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Keep in mind the relationship of Current to Brightness will be miserably non-linear.  S.

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Keep in mind the relationship of Current to Brightness will be miserably non-linear.  S.

The output should track the current over a fairly wide range.  At the extreme end the curve will flatten out.  Otherwise, doubling the current should double the output.

Keep in mind, doubling the output does not mean it appears twice as bright---the eye is nonlinear & adaptive.  

 

Hmmmm... Maybe if we cut all of our bright lites to half power, we'd adapt & see just as well as with all of our blazing lights at night.

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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Scroungre wrote:

Keep in mind the relationship of Current to Brightness will be miserably non-linear.  S.

 

It doesn't look *that* bad, according to the datasheet. You aren't supposed to go over 700 mA, anyway, and that's where linearity seems to breakdown more.

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I give up...

 

I Googled Luminous,

Then Luminous Flux

Then Luminous Energy,

Then Brightness,

Then Lightness,

Then Radiance,

.

.

.

Then I gave up and decided its a good thing I'm not studying this for a physics class.

 

I tend to agree with Scroungre on this, if one sets up a simple PWM for an LED from 0 % to 100% what I perceive as how bright the LED is, (regardless of the actual scientific term for it), is very non-linear.

It also varies with the background lighting, (i.e. am I viewing the LED in the dash of a car at night, or in a well lit room, or in sun light...).

 

Perhaps this LED was optimized for its current to perceived brightness transfer function, but the OP ought to wire up a simple PWM and view the specific LED if this is going to matter for the overall project.

If it does matter, a simple look-up table can easily correct for the non-linearity.

 

JC

 

 

 

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The output power is simply proportional to current, just like a laser diode.  There is an initial knee then it will be fairly linear over a wide range, then will top out at its max output level& give no more  (extra drive is just extra heat).

The datasheets don't care about our,eyes since they are about the worst detector possible, in terms of any calibration constant...in fact, just the opposite of any consistency.

 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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d

Doing magic with a USD 7 Logic Analyser: https://www.avrfreaks.net/comment/2421756#comment-2421756

Bunch of old projects with AVR's: http://www.hoevendesign.com

Last Edited: Mon. Jun 24, 2019 - 08:59 AM
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Vindhyachal Takniki wrote:

1. Need to drive a single white led, part no: 2ES103CW06000001 , datasheet: http://www.edison-opto.com/en/pr...

Datasheet says it has Vf=3.4V & If=700mA, Peak pulse current: 1A

Intensity needs to be varied from 0 to 100%.

 

2. Want to know, suppose I want to glow led at 100%, should I give maxium 3.4V/700mA  or I can increase voltage or current further for high intensity? If yes, how to calcualte maximum recommended values for safe operation

 

LEDs are designed to be current driven, so you would design 700mA and the '3.4V' is whatever that particular LED drops, at that temperature.

You can go above 700mA with more aggressive cooling, or accepting a shorter life span.

For that, check the cooling they used to spec 700mA, and then as you improve that cooling, higher currents can give the same die temperature.

Sounds like they spec 1A peak, so there is not that much headroom to play with.

 

 

Note that better cooling will give higher brightness, merely from the cooling effect alone  :)  

 

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d

Doing magic with a USD 7 Logic Analyser: https://www.avrfreaks.net/comment/2421756#comment-2421756

Bunch of old projects with AVR's: http://www.hoevendesign.com

Last Edited: Mon. Jun 24, 2019 - 09:00 AM
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Who-me wrote:
Note that better cooling will give higher brightness, merely from the cooling effect alone  :)  

 

I guess that's related to the higher junction voltage at low temperatures, resulting in higher power for the same current. Apparently this increased power translates to more light (kinda makes sense).

Last Edited: Tue. Jun 4, 2019 - 12:12 AM
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d

Doing magic with a USD 7 Logic Analyser: https://www.avrfreaks.net/comment/2421756#comment-2421756

Bunch of old projects with AVR's: http://www.hoevendesign.com

Last Edited: Mon. Jun 24, 2019 - 09:00 AM
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El Tangas wrote:

Scroungre wrote:

 

Keep in mind the relationship of Current to Brightness will be miserably non-linear.  S.

It doesn't look *that* bad, according to the datasheet. You aren't supposed to go over 700 mA, anyway, and that's where linearity seems to breakdown more.

 

Note that your graph only goes down to 0.6.  The OP wanted to go to 0.0...  I can't imagine it's real linear off either end, and as has also been pointed out, eyes aren't real linear either.  S.

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The red lifetime curve seems to be increasing 17% per each 10 ºC cooler. This would give about 250,000 hours at room temperature*.

 

* 20-25 ºC.

Last Edited: Tue. Jun 4, 2019 - 02:25 PM
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Maybe well know in:

>> 250000/365/24
ans =  28.539  [years]

 

Weird thing though is a 25% difference in lifetime for the same junction temperature depending on air temperature.

But the exact numbers do not matter much, especially as the graph is from another brand of LED's.

The main thing is that hot leds have a significantly reduced life expectancy.

 

Doing magic with a USD 7 Logic Analyser: https://www.avrfreaks.net/comment/2421756#comment-2421756

Bunch of old projects with AVR's: http://www.hoevendesign.com

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I have been driving it at 700mAh with ease at good brigtness & able to vary to 0% also

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I don’t think you were driving the led at 700mAh - your meter must’ve been lying to you.
We really didn’t move things forward did we?

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700mAh is a capacity - it means enough energy to supply 700mA for an hour. I presume the 'h' was a mis-typed character?