# Help me understand...LED Wattage ratings?



## lightime (Aug 17, 2009)

Ok, I am new to the led game so I know this is a very basic question.

I see high power led's/emitters sometimes called 1watt or 3watt (I think I have seen 10watt led also) but how do they come up with this wattage rating? I thought it wasn't until you decided what current you would run them at that you would determine the wattage... so that if you were to drive at 350ma, 700ma, or 1000ma for example, they would be a different wattage in each application.

What "wattage" is a Cree XRE Q5, SSC P4, considered? I guess these are called 3watt?

Thanks guys!


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## aljsk8 (Aug 17, 2009)

watts is volts x amps

so lets stay cree xre and you are pushing it at 1amp the forward voltage will be about 3.7v

1 x 3.7 = 3.7w

lets say you run it at 350ma Vf will be say 3.3

0.35 x 3.3 = 1.155w

the wattage ratings can range from maximum or at binned levels (350ma or 700ma) or it can sometimes just be some made up number

hope that helps


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## lightime (Aug 17, 2009)

Thanks for the reply. That's what I was figuring...you don't know the wattage until you actually use the led in an application and decide on what current you will use. 

It's just that sometimes I see lights that say they have "three 3 watt leds" and when you look at them carefully they may have what appear to be Cree XRE or Luxeon etc...but they are calling them 3 watt leds.


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## evilc66 (Aug 17, 2009)

It's just a simple dumbed down way to rate and group the LEDs power handling capabilities. You are right though. The true wattage isn't seen until you decide on your drive current.


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## bhvm (Aug 17, 2009)

I see that 'One watt' and 'Three Watt' misnomers came actually as a de-generation from High power LED pioneer- Ailgent-Phillips (AKA Luxeon).

Their Luxeon 1 and Luxeon III had were somehow begun the trend of 1W and 3W.

Actual 1W LED is 1.242 watts (3.5v X 350 mA)
Actual 3W LED is 2.44 Watts (3.5v X 700mA)

Please note that a 3W LED is not exactly triple, but more like Double of a 1W LED


Chinese have come up with Blinding 10W....20W...100w and even 500W!! LED modules!
They are something like a matrix of 1W LEDs in Series-Parallel.


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## lightime (Aug 18, 2009)

hmm...so we can trace this legacy back to the Luxeons then...that makes sense in that they were actually called "I" and "III". Very interesting...


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## Lynx_Arc (Aug 18, 2009)

with proper heatsinking many LEDs can be driven beyone *nominal* power ratings at the expense of LED life. I have a 1 watt LED driven at close to 1 amp or 3 watts and people have driven crees at power about 4watts. These days LEDs are improving more often unlike the slow evolution of the 1 watt -> 3 watts there have been more increments so the wattage I.D. system is no longer useful as a bin 6 months later can output more light at the same wattage you cannot compare one to another using such a simple system there are too many *flavors* of LEDs now.


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## bhvm (Aug 20, 2009)

IMHO.

3W are just better 'bin' 1w ones.
They use the same die.. and same vF.
They can tolerate more mA than 1W...and also have lower vF at SAME mA. They are just a better batch of 1W i see..


This way, we will soon have 5W and even 10 W single die LEDs that'll be superbly efficient.


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