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Why does luxeon led neea a driver circuit??

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antoniodilen

New Member
Hi everybody,
need little help understanding how these POWER LED's work...
all i know is that they are much brighter than the average leds...
so if any body has time please teach me about these led's...
and why they need driver circuits..
many thnks in advance:)

(sorry...i have made a spelling mistake on the thread heading)
 
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Sceadwian

Banned
They're just like any other LED. You just need to limit the current going to them. I think they're more sensitive to forward voltage drop variations so constant current circuits are often used instead of resistors.
 

antoniodilen

New Member
Do they generate a lot of heat too?
is there a simple way to drive them ???
is it possible to drive many with a 12v supply as we drive a few normal led's in series?
 

Sceadwian

Banned
Yes, they generate heat, for their full rated power I think they often need to be heat sinked. The cooler you keep them the longer they live. You can drive them with resistors just like any other LED, but you're dealing with more power so the resistors will be generating heat too, resistors change value when heated. Basically you just have to be more careful than with a low power LED.
 

antoniodilen

New Member
Yes, they generate heat, for their full rated power I think they often need to be heat sinked. The cooler you keep them the longer they live. You can drive them with resistors just like any other LED, but you're dealing with more power so the resistors will be generating heat too, resistors change value when heated. Basically you just have to be more careful than with a low power LED.
Thanks again:)
 

audioguru

Well-Known Member
Most Helpful Member
I think the forward voltage of the high power LED drops as it heats which causes thermal runaway. Heat makes more current which makes more heat which makes more current then KABOOM! You can't see the LED when it is smoking.

Use a constant current driver instead of a simple resistor.
 

Sceadwian

Banned
Or value the resistor conservatively.. which will limit your initial brightness.
That's pretty much why they need drivers =)
 

Hero999

Banned
They're just like any other LED. You just need to limit the current going to them. I think they're more sensitive to forward voltage drop variations so constant current circuits are often used instead of resistors.
I think it's more an efficiency thing: there's no point in paying a lot for an expensive efficient LED and wasting over half the power in a resistor which also requires a large heat sink.

It you don't need current regulation then a good way of driving a power LED is to just use an oscillator (e.g. a 555 timer), MOSFET, Schottky diode and inductor - it's cheap, efficient and achieves similar current regulation to a resistor.

How much current does the LED require? Don't give the absolute maximum rating, give the recommended operating current.

What's the typical forward voltage?

What's the voltage range of your power supply?
 

Ubergeek63

Well-Known Member
I think it's more an efficiency thing: there's no point in paying a lot for an expensive efficient LED and wasting over half the power in a resistor which also requires a large heat sink.
Actually 100Lm/W with a series resistor can still be more efficient than junk LEDs.

I would still use a good driver.
 

antoniodilen

New Member
I think the forward voltage of the high power LED drops as it heats which causes thermal runaway. Heat makes more current which makes more heat which makes more current then KABOOM! You can't see the LED when it is smoking.

Use a constant current driver instead of a simple resistor.
...thank you for your time
 

antoniodilen

New Member
I think it's more an efficiency thing: there's no point in paying a lot for an expensive efficient LED and wasting over half the power in a resistor which also requires a large heat sink.

It you don't need current regulation then a good way of driving a power LED is to just use an oscillator (e.g. a 555 timer), MOSFET, Schottky diode and inductor - it's cheap, efficient and achieves similar current regulation to a resistor.

How much current does the LED require? Don't give the absolute maximum rating, give the recommended operating current.

What's the typical forward voltage?

What's the voltage range of your power supply?
i'm planning on driving them with a 12V supply...
thanks i got some driver's from older threads posted in this site
 

Sceadwian

Banned
Expensive drive, but a lot of features, well suited for expensive leds =)
 
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