Cree Easy White???

[Aepoc]

Can anybody explain the difference between Cree's Easy White LEDs and all others? Cree's website states that they "eliminate chromaticity binning and enables luminaire manufacturers to deliver consistent color and high efficacy light output of a multi-die LED" It also states that they reduce LED to LED color variation...

Does the first part simply mean that Cree has refined their manufacturing process to be extremely accurate with respect to achieving chromaticity ranges? If so, why can't they apply this to all of the LEDs they currently produce...

Also, can't one reduce the LED to LED color variation by selecting the appropriate chromaticity bin when purchasing the LEDs?

Lastly, at least with the XM-L LED's, the Easy White emitters are 4 separate phosphorous pads, while the standard XM-L emitters are one pad...

Please help me seek a clearer understanding of how this Easy White differs from other Cree products... When would one use these over the standard LEDs?

 

[Harold_B]

If I recall correctly the Easy White's are all multiple die (like the XM-L example you mention) because what they are doing is mixing and matching the die / phosphor arrays for narrow color temperature. Yes you can get that by binning but that's one of the benefits of the Easy White - no binning. The multiple die also makes driver electronics easier to design for luminaires.

 

[Aepoc]

Okay, so the no binning is where the "easy" comes from... How does it make the drivers easier to design?

 

[Harold_B]

First I'll say that I'm not an electronics guy, but my understanding is that it is easier to design a driver for a circuit of four die driven in series (high voltage, low current) than one big die like the standard XM-L (low voltage, high current) in particular for 110VAC to DC. Perhaps not so much "easier" as in difficulty but as in more robust over time.

 

[onetrickpony]

If I recall correctly the Easy White's are all multiple die (like the XM-L example you mention) because what they are doing is mixing and matching the die / phosphor arrays for narrow color temperature. Yes you can get that by binning but that's one of the benefits of the Easy White - no binning. The multiple die also makes driver electronics easier to design for luminaires.

When you say XM-L, do you mean MP-L? XM-L's are single die.

 

[Harold_B]

Nope. XM-L Easy White: http://www.cree.com/products/pdf/XLampXM-L_EZW.pdf

 

[CKOD]

When you say XM-L, do you mean MP-L? XM-L's are single die.

Not XM-L easy whites, they even come in the U3 bin IIRC, 4 XP-E dies it looks like (EZ-1000 or EZ-900 IIRC)

First I'll say that I'm not an electronics guy, but my understanding is that it is easier to design a driver for a circuit of four die driven in series (high voltage, low current) than one big die like the standard XM-L (low voltage, high current) in particular for 110VAC to DC. Perhaps not so much "easier" as in difficulty but as in more robust over time.

Youre on the right track, when it comes to semiconductor stuff, for low voltage stuff (<50-60v ish) voltage handling capability is cheap and current handling capability is more pricy, in both efficiency losses, and part costs. Not only that, there already exists 350mA, 700mA, 1000mA, 1500mA constant current LED drivers with a universal AC input(11 on mouser, 39 on digikey atm) . For someone making a light fixture, an off the shelf solution for a ballast would be preferable to having to design one. Not only that, if the ballast has various certification (CE, UL, etc... ) and the output is <60v, then all the other wiring is low voltage per NEC, and in the US at least, that would make safety certification cheaper and easier.

For bulk, flood lighting, I doubt pricy, high powered, large die LEDs will gain popularity. But they do have their purpose, as we know.

 

[onetrickpony]

I didn't even know 'bout those, thanks for the heads up!

EDIT: The typical XM-L is single die, why didn't CREE make a somewhat different model name for this? Talk about confusing....

 

[Harold_B]

No doubt it's confusing. All I can see is that the package is the same (5 X 5 mm with a 3 mm dome).

 

[Aepoc]

Okay so they are better for fixed lighting... Would you ever want to use one of these over a standard XM-L for a flashlight?

Also, my experience is that one only needs to regulate current for an LED provided the voltage is within the range of the current regulator... Why does cree reference different voltages (6v and 12v) in their data sheet? Does one have to regulate the voltage that is sent to these LEDs? Why would anybody choose 12v over 6v... the difference in luminous flux @ 700mA is so small...

 

[onetrickpony]

Okay so they are better for fixed lighting... Would you ever want to use one of these over a standard XM-L for a flashlight?

Also, my experience is that one only needs to regulate current for an LED provided the voltage is within the range of the current regulator... Why does cree reference different voltages (6v and 12v) in their data sheet? Does one have to regulate the voltage that is sent to these LEDs? Why would anybody choose 12v over 6v... the difference in luminous flux @ 700mA is so small...

I think they are two separate products that you can order, one with a Vf of 6, one with 12. I could be wrong, but that's my best guess.

 

[Microa]

There are 4 dies inside. The 6V model is connected 2S2P and the 12V model is connected 4S1P.

 

[panicmechanic]

If I recall correctly the Easy White's are all multiple die (like the XM-L example you mention) because what they are doing is mixing and matching the die / phosphor arrays for narrow color temperature.

Nope, Easy White is just a narrower binning range, so designers don't have to worry about having different colors in multi-emitter setups.
Only the XM-L Easy White in 6V or 12V configurations are multi-chip devices, but I guess a single-chip Easy White XM-L @ 3V will also be available.
So confusing, even Cutter sells them without even telling if you're buying a 6V or a 12V version. I would like to buy one, but without info?

 

[Harold_B]

Cree had published a short paper on color mixing where they mention that "Cree performs the color mixing on behalf of it's customers in building EasyWhite versions....". My understanding from the sales rep was that they mix and match at the factory to achieve the narrower bins. I am always wiling to be wrong!

 

[panicmechanic]

My understanding from the sales rep was that they mix and match at the factory to achieve the narrower bins. I am always wiling to be wrong!

You may be right, I did not find proof for my above claims. I thought I had seen the Easy White binning on single dies.
Sorry for the confusion!

 

[CuriousOne]

I recently bough 1250lm 3500k easywhite assembly (pre-assembled in-ceiling mount fixture+driver) and would like to say that it rocks!

So pleasant, warm color with no color distortions or pop-up. It's tonal curve resembles autumn midday sun - not as white as summers one, but still very pleasant, golden toned. I've did a side by side comparison with similarily rated Philips led bulb - cree won easilly.

 

[WeLight]

In defense we actually have emitters listed by voltage, cri and Macadams steps. Not sure if its clear but Cree mix single die bins x 4 to nail the CCT so that each one you buy is identical

 

[SemiMan]

Cree Easywhite are all multi-die packages. This is different from selecting a single bin and hoping you can buy that bin again. This guarantees you a color point, not simple CCT, but a color point on the blackbody curve. I think only Lumileds is offering single emitters with tight binning at this point. They have different phosphor technology and better control.

Semiman

 

[Anders Hoveland]

I wish they had a way of varying the overal color, besides just adjusting the ratio of the (orange) phosphor to the blue peak emission. When you only have a single variable ratio, the possible color range will be quite limited.

Although they have developed a phosphor that emits more to the greener side. They are already using these in some of the LED downlights, so that the separate red LED chips do not throw off the overal color. I think it is called bright blends, or something like that, I'm sure someone more knowledged will know what I am referring to.

 

[SemiMan]

I wish they had a way of varying the overal color, besides just adjusting the ratio of the (orange) phosphor to the blue peak emission. When you only have a single variable ratio, the possible color range will be quite limited.

Although they have developed a phosphor that emits more to the greener side. They are already using these in some of the LED downlights, so that the separate red LED chips do not throw off the overal color. I think it is called bright blends, or something like that, I'm sure someone more knowledged will know what I am referring to.

There are several different phosphor combinations that are used and high CRI lamps use multiple phosphors, not a single phosphor. There are phosphor based on different technology that are tunable, the only issue is that they are not as efficient and hence have not seen great commercial success.

Semiman