Hello!
A few days ago I was shopping on eBay and found 3watt yellow "star" leds.
On the description page, it was rated at 2.0volts - 2.4v and 750ma. If I multiply those , I get about 1.8 watts.
Am I doing something doing wrong with the calculation?

 

Am I doing something doing wrong with the calculation?

Nope. The discrepancy rests elsewhere.

 

Most likely it's the typical overrated chinese (or whatever) marketing.


Over in "my realm" of car audio,we deal with this all the time. You'll buy an amplifier rated for 1100 watts but only has 30 amps worth of fusing and can only put out a measured 2xx watts. Rounding up, inflating numbers, etc to make a product look better than it really is

 

Aww... So the maximum is only 1.8 watts I guess...

 

Most likely it's the typical overrated chinese (or whatever) marketing.

I have seen some really awful data sheets for Chinese LED's. Some were so bad that there was no way to know what they were trying to sell. I think a lot of the problem was in the translation to English.

Giving them the benefit of the doubt, it may be that it is simply a typo caused by editing a data sheet that was originally for a white LED -- 750 mA times 3.6 volts is almost 3 watts.

 

Most likely it's the typical overrated chinese (or whatever) marketing.


Over in "my realm" of car audio,we deal with this all the time. You'll buy an amplifier rated for 1100 watts but only has 30 amps worth of fusing and can only put out a measured 2xx watts. Rounding up, inflating numbers, etc to make a product look better than it really is

I remember just a few years ago, there was a big stink about the HP ratings of small combustion engines.
Such as rating a 12 HP, @20 HP, etc.

 

Well, here's the datasheet http://lighthouseleds.com/downloads/dl/file/id/28/3_watt_yellow_star_led_datasheet.pdf

 

Hello!
A few days ago I was shopping on eBay and found 3watt yellow "star" leds.
On the description page, it was rated at 2.0volts - 2.4v and 750ma. If I multiply those , I get about 1.8 watts.
Am I doing something doing wrong with the calculation?

The 3W is almost certainly what is called an "abs max" rating for power dissipation for the device which is defined primarily by the die size and package type. Obviously, the nominal operating conditions better be less than the absolute maximum ratings or it smokes. The power is not what you care about, it's the luminance (brightness). In fact, if it puts out the same light at a LOWER power that's actually better because it runs cooler and eats less power.