# Searching the most efficiant warm white LED chip



## Mkala (Sep 6, 2010)

Hello !

I'am searching the best efficient LED chip available today in Warm White.

I plan to modify a standard light fixture for the living room, the goal is to obtain about 1500 lumens.

Some characteristics that I am searching :

- warm white (3000-3500 °k)
- highest efficiency
- high CRI ( >= 80)
- wide viewing angle (>= 120°)

Which LED chip should I use for this application ?

Any help, links, idee greatly appreciated 

Thank you


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## John_Galt (Sep 6, 2010)

Check out the XP-G, it is currently the most efficient LED available.


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## Mkala (Sep 7, 2010)

Thank for your reply John

Took from datasheet :

Warm White (CCT range 2,600 - 3,700 K)

[email protected] = 3V
[email protected] = 3V * 0.35A = 1.05W

[email protected] = 3.2V
[email protected] = 3.2V * 0.70A = 2.24W
Lumen @ 700mA = ~185% of [email protected]

[email protected] = 3.3V
[email protected] = 3.3V * 1.00A = 3.3W
Lumen @ 1000mA = 250% of LM[email protected]

Efficiency :

```
BIN    [email protected]   LM/[email protected] LM/[email protected] LM/[email protected]
Q3        94           89         78         71
Q4       100           95         83         76
Q5       107           102        88         81
```
Number of chip to achieve ~1500 LM :


Choice : bin Q4 (for exemple)

```
Current       Flux (LM)   Nb chips for ~1500LM
350              100              15
700              185               8
1000             250               6
```
Efficiency is realy good at 350mA, but this mean a lot of chip... 700mA is a good compromise I think. Someone know a better power LED chip ?

Now, I need to find XP-G warm white at a good price (available in europe), if you have a good advice tell me 

I need to find thermal board, or designing one. If you know board with 9 chip (3x3 I think this can exist) 

I will search more info, if you have idee / links help me 
Thanks


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## csshih (Sep 7, 2010)

efficacy is high, but those cree warm white bins don't have a very high CRI. perhaps it is better to mix red and cool white emitters together?


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## Mkala (Sep 7, 2010)

In the datasheet, the highest CRI is 80 (typical), which is for warm white.

Cool white CRI is 75.

Do you think that cool white LEDs with some red chip are better for rendering ?


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## deadrx7conv (Sep 7, 2010)

Read thru the fixed lighting forum.


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## WeLight (Sep 9, 2010)

We have customers using Q5 in E7 bin getting 86 CRI on average


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## -Gast- (Sep 9, 2010)

Im using a xp-g Q5 7D. Its really nice.

But i cant measure cri here....


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## jason 77 (Sep 9, 2010)

Not sure if they are as efficient as the cree's but since they are multichip arrays they put out a lot more light, take a look at the bridgelux es series...

http://www.bridgelux.com/products/ledarray_es.html


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## deadrx7conv (Sep 9, 2010)

Add one red LED to your XPG LED array and CRI should be fine. 

This website is excellent. Read through all the links here:
http://darelldd.com/light/0_fixed_lighting.htm

If I had the time, patience, and money, I'd have this closet light in EVERY room: http://darelldd.com/light/closet_light.html

Bridgelux seems to be the best choice for home fixture retrofitting. 

High CRI and high efficiency are words not used too well together. 

http://www.ledsmagazine.com/products/23186
http://www.philipslumileds.com/products/luxeon-rebel/luxeon-rebel-white
http://www.cree.com/products/pdf/xlamp7090xr-e.pdf
http://www.cree.com/products/xlamp_mpl.asp
https://www.candlepowerforums.com/threads/199054
https://www.candlepowerforums.com/threads/252922
https://www.candlepowerforums.com/threads/202363

Good read. 
https://www.candlepowerforums.com/threads/89607
Efficiency drops as power to LED increases. So, more chips equals more lighting efficiency. CRI drops as lumens/watt increases. So you have to find the balance you want among lumens-watts-CRI. 

I think that you're better off with a couple Bridgelux, Cree MC-E's, or Seoul P7's driven to the light output you want. Add a red, cyan, and/or blue LEDs to up the CRI as needed. Your best bet is to find a local supplier or ebay for LEDs since buying a dozen/shipping can be costly. 

And, read the fixed lighting forum here. You can quickly scroll through the pages to see the retrofits that some have created.
http://www.candlepowerforums.com/vb/forumdisplay.php?f=89


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## blasterman (Sep 10, 2010)

> Do you think that cool white LEDs with some red chip are better for rendering ?


 
{pounds head on desk}

No. Mixing a cool-white and a red LED together will yield a pink looking light with less CRI than a warm. You need to mix *amber* and red to make this work, and it's not worth the trouble and will produce less efficiency than a WW XP-G. Plus, cool-white LEDs cover a range from 7000k to 5300k, and just adding red in would yield goofy results anyways. A warm white LED is not a cool-white with red added. Much, much more complex that that.

The newer Bridgelux are barely 80 lumens per watt in warm-white. Not a design option if efficiency is a top requirement. Bridgelux are typically the best resource when you need lots of light for low cost and few LEDs. A pair of 802's - big heat sink and driver - done.

Top bin XP-G's should *easily* solve this problem, and the warm white versions have solid CRI not worth bickering about. If we were talking neutrals we could be chatting about rebels and such.


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## RedmEx (Sep 10, 2010)

blasterman said:


> You need to mix *amber* and red to make this work, and it's not worth the trouble and will produce less efficiency than a WW XP-G.



I can confirm the first part of blastermans statement. Cree has produced a lamp especially dedicated for that purpose.
http://cree.com/products/modules.asp
I consists of 5 unsaturated amber and tree saturated red leds see this video:

http://www.youtube.com/watch?v=KXJ7f9r6G_I

At least Cree expects customers for this type of led modules.

So if your focus is on really warm white colors below 3000 K, this might be the best choice, if you go for highest efficiency you should also look at the Cree MP-L, delivering 800 lumens from a single emitter (consisting of 24 dies) at 10 Watts, but with proper cooling it can handle up to 20 Watts.
This is not the most efficient LED but perhaps the most *cost efficient* if you include optics and secondary electronics.

http://candlepowerforums.com/vb/showthread.php?t=287234


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## deadrx7conv (Sep 10, 2010)

It wasn't mixing "a" red with "a" white LED. The single red LED with several of the white LEDs seems to bring out the color. From the pics in the links, sorry I just don't see the pink.

No pink in the last pictures here:
http://darelldd.com/light/closet_light.html
or here:
http://darelldd.com/light/refrigerator_led.htm
looks good here too:
http://darelldd.com/light/garage_opener.html

I also don't care for overly high CRI jaundiced LEDs. They just don't look right. Too yellowy and pasty. Incans do a better job. Since I don't have construction paper laid out on the floor, and the decorations here are pretty drab, the lower CRI LEDs work well for me here. I prefer the 'hospital' white look. But a tad more color is all I needed, and probably why the XPG-R5's are sitting on the table and not in a fixture, while I'm awaiting several colored LEDs to see what works for me. 

Another ratio of LEDs. 
https://www.candlepowerforums.com/posts/3028162
https://www.candlepowerforums.com/threads/279082
http://candlepowerforums.com/vb/showthread.php?p=3508263
https://www.candlepowerforums.com/threads/248590

Maybe its best to find a single LED with the lumens/watt plus CRI to make the thread starter happy. But, the option of adding a colored LED to assist, whether they be yellow, amber, red, blue, green or cyan. Only after the light is built and tested, will it be known if it worked or needs adjustment for the location it'll be used in.


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## blasterman (Sep 10, 2010)

> From the pics in the links, sorry I just don't see the pink.


 
Which simply means the camera was set to 'auto'. I can take a picture of my reef tank which runs at 16,000k with the same camera and you likely won't see blue either. The posts you linked didn't specific what bin/flux the LEDs were either, and don't conclude much. To be honest, some of the colors look crappy and under-saturated.

*Cool-white + red = pink.* While adding a bit of red to a WG cool-white helps color rendition, it's not the same as a warm-white or neutral emitter. If all it took were mixing red with a cool white Cree would be doing this with their own fixtures and not bothering with neutral white emitters at all which are expensive and tricky to produce. 

However, if you start with a lower K bin of cool-white, and add some amber and red to it via personal preference, you will end up with a nice light that suits your taste. 



> I also don't care for overly high CRI jaundiced LEDs. They just don't look right. Too yellowy and pasty.


 I haven't spent much time with high CRI emitters, but I've yet to see a warm-white LED of any brand produce the excessive green-yellow of an incan. Warm-whites simply can't produce the yellow of an incan without being absurdly inefficient.

The last couple of doctors offices I was in along with a local hospital were using high K +90 CRI daylight fluorescent tubes. Contrary to the typical Cree bunk, a cool white 70CRI LED doesn't equal a high CRI daylight fluorescent. The really high end +95CRI tubes I've been around were just like working under a sunny sky without the glare.

Regardless, the OP will do just fine with regular warm-white LEDs. There's no reason to mix or dink around with it.


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## Th232 (Sep 10, 2010)

deadrx7conv said:


> I also don't care for overly high CRI jaundiced LEDs.



Is it the high CRI you don't like, or the low CCT that usually comes along with the high CRI LEDs we see around here most often? The higher CCT high CRI LEDs I've played with are most definitely not jaundiced.


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## Mkala (Sep 13, 2010)

Thank you all for these links, infos, good thread and many more. 

deadrx7conv > In the past I have eliminated Bridgelux because they was not the most efficient.
But, this was not a good calculation, as we can see in my second post, -unless I buy a many many emitter to drive them at 1W each - I have the same efficiency than Bridgelux : ~80lm/w.
So Bridgelux could be a good solution.

The site of darelldd.com is very interesting !

The new Rebel ES from Lumiled look promising :

http://www.philipslumileds.com/products/luxeon-rebel/luxeon-rebel-white/luxeon-rebel-es

300lm @ 3.1w... 5 units for the 1500 lumens and with a LED efficiency of 97lm/w ! But the CRI is only at 60min / 70 typ and the CCT is 4100...

I must choose if I start with XPGs or Bridgelux. After, following rendering, will see what I should do if needed to improve the light.


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## Mkala (Sep 22, 2010)

I have compared the chips from Bridgelux, the most interesting for my application is the BXRA-W1202.

Flux, power and efficiency at some drive currents :

```
Flux LM    Vf   Current    Power W    Efficiency LM/W
 820    14.4    0.70          10.08    81.35
1180    14.9    1.05          15.65    75.42
1320    15.1    1.20          18.12    72.85
1510    15.4    1.40          21.56    70.04
1820    15.8    1.75          27.65    65.82
```
The efficiency is a bit lower than XP-G, but the price is interesting.

I have also found a board with 7 XP-G Q5 :







http://www.led-tech.de/en/High-Powe...REE-XP-G-Q5-on-round-PCB-LT-1705_120_117.html

Same as above, I must chose now


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## Mkala (Apr 20, 2011)

Hi all 

Since my last post, I have not do anything.. but I have continued to search interesant warm white LED chip.

Some weeks ago, Cree (one more time  ) has released the warm white version of the cree XM-L.

This LED has high efficiency and high power capability, here for T3 bin at 2600-3700 K range :



```
Flux LM    Vf   Current    Power W    Efficiency LM/W
 220     2.9    0.70           2.03   108.37
 429     3.1    1.50           4.65    92.30
 715     3.35   3.00          10.05    71.14
```
www.led-tech.de have released this module, looks interesting for my 1500lm target :






To achive this target, I must run the module at 1.8A. At this current, the vF should be 3.15V, so 1.8 * 3.15 *3 = 88.18 lm/w
CRI is at about 80.

Now I must choose a driver for this module. Whether I use a standard driver with PVM for dimming, or I made a more efficient driver which use lower current (to maximize efficiency) for dimmed output and higher current for high output.
If you have advices about chips, solution, feel free to post it 

Thank you


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## Oznog (Apr 21, 2011)

The warm white XML has been around for many months.

KD/DX carries them- cheap.

You should be concerned in multi-device MCPCBs about the extra heat and higher die temps. Of course heat is a concern in single-device boards too, but they do usually reduce the transfer cross-section in favor of more devices in these.

IIRC the XML datasheets are actually overly conservative in their Vf ratings. They're typically better (lower) than stated.

Cooling really is a big issue at these power levels, especially if you're splitting hairs going for "the best".


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## zzonbi (Apr 23, 2011)

"The warm white XML has been around for many months.

KD/DX carries them- cheap."

I didn't see them. Could you please post their links/SKUs?


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## Microa (Apr 23, 2011)

This latest LED may be of your interest for standard lighting fixture.
http://www.cree.com/products/pdf/XLampXM-L_EZW.pdf


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## Oznog (Apr 24, 2011)

Well DX's SKU #51989 I got seemed pretty yellowish compared to the #50599 which was more of a bluish white. OK, yeah, the T2-T3 on the Cree datasheet at the "warm white", I see. Maybe I wasn't seeing the color correctly, maybe DX was sending a warm, or at least a neutral, out under the wrong part #- which is easy to see since Cree puts nothing on the LED itself to identify them.


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## Mkala (May 2, 2011)

Oznog, thank you for your reply.
I am in Europe What is KD/DX ? DX= DealExtreme ? I have not found Warm white Cree chip led on it.

Cooling should not be an issue for my light, comparing to a flash light I can use a huge heatsink to cool it.


Microa, thanks, looks intersting. One good thing is that the voltage is higher and current lower. It is more easy to find AC/DC supplies with low current (350-700mA).
But this chip is more difficult to find, I will see if I can get it.


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## zzonbi (May 21, 2011)

me neither, but check out cxa2011: far from the wishful lab lm/W, but nice lm/$ (some 3000lm for 15$)... cree is king when it comes to cheap lumens


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## Mkala (May 23, 2011)

Thank you for this idea !

But -as you say- lumens/w is not very interesting. At nominal drive current, we are about a 70lm/w, but at output I need (about 1500lm) we are already lower at about 60 lm/w.

This weekend I have ordered XM-L module (see above), XM-L alone and XP-E high CRI (> 90) to do some tests


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## MWClint (May 23, 2011)

Mouser.com has the T2 Bin Seoul, 93 CRI, Neutral whites, 4000K 88-91 lm/w
I have been using 20 of these leds all spring to grow tomato plants from seed, indoors.
i'm using 5 leds in series epoxied to an aluminum carpet trim bar(5$ home depot) driven by a surplus 16.6v laptop power supply. each led is seeing ~550mah.
built 4 of these and they have been running 8-12 hours per day. finished building a stone retaining wall raised garden yesterday, and with the
weather warming up, i'll be transplanting them all outdoors.



Mouser Part #: 889-S4218006T2EL 
Manufacturer Part #: S42180-06-T2-EL
Manufacturer: Seoul Semiconductor 
Description: LED High Power (> 0.5 Watts) Natural White 4000K 3.8W, 88-91lm


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## Mkala (May 24, 2011)

Thank you for these informations, this one can be intersting too !

The CRI (typical) is very good, but when the CRI is good the efficiency is generally not the best :

For your 4000k / 93 CRI LED, claimed output is 76lm @ 3.3V / 0.35A (=1.15W) => 65lm / w

But we cant have all, rendering should be very good. Do you have pics ?


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## zzonbi (May 24, 2011)

I stand by the cxa, on paper it's 83lm/W nominal, for 3000K/cri80 
But we should compare at equal lm/$: by choosing 50lm/$ drive level you get 100lm/W, if we equalise temperatures too, ie Tj 25C. Anyway thermal resistance is very low, 0.4C/W, so 85C seems overkill.


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## MWClint (May 24, 2011)

Mkala said:


> For your 4000k / 93 CRI LED, claimed output is 76lm @ 3.3V / 0.35A (=1.15W) => 65lm / w


 
hmm, thats an old typo on mouser's site thats been there since they hosted S2 bins.
these are T2 bin which are 88-91lm, which is written on their site, i also verified by calling them and having them check the bin on their packaging.

here's a screen of the leds i'm talking about. 





but when you click on it, you see the old S2 spec typo. I told them about it..but they havent fixed it yet.


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## Mkala (May 25, 2011)

Ha yes, you are right !

T2 bin = 80-91 lm. I take the middle, 85. Divided by 1.15W => 74lm /w.

Quite good


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## Mkala (Jun 24, 2011)

I finally received my package! The delivery company has lost the first one... After, LED-Tech has re-send it quickly and now I have my LEDs !






Top left : 3x Cree XM-L T3
Top right : Cree MX 3
Bottom left : Cree XP-E high CRI
Bottom right : Cree XM-L T3

Today, drilled and tapped the heatsink :











It is a little too big.. but it is better as a little to small.

All mounted :






Next, I will do some tests to find the luminous flux I need, and with this choose the operating current.
After this I can chose and design the electronics.

:wave:


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## deadrx7conv (Jun 24, 2011)

Too funny with led-tech.de since my shipment was also lost or mis-shipped... They resent them but wish they'd get their 'shipping act' together. My original shipment's tracking number bounced all over Europe for a couple weeks. 

Thats a nice simple light build. The bigger the heatsink is, the better!!! Many tend to go too little. But, I would have sanded/lapped/polished the heatsink area before mounting the LED. 

Triple XML should produce a ton of light. What drivers, power supply, or batteries are you using?


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## Mkala (Jun 26, 2011)

So I am not alone ! Delivred by GLS too ??

Yes I could improve the thermal transfert with a polished heatsink.

I am building a light for the living room, then powered from the mains. The driver for the moment I don't know, I have two choice :

a) Linkswitch-PH from PowerInt (http://www.powerint.com/products/linkswitch-family/linkswitch-ph)
AC/DC IC designed for LED driving. Dimmable with standard triac dimmer. The hard side is to build the transformer...

a) Standard AC/DC PSU, with DC current regulation / dimming. The positive point is I can reduce current in the LEDs to improve efficiency at low illumination needs. But I think the overall efficiency will be lower, even with two good circuit (AC/DC and DC current source / dimmer) at 90% efficiency each, it will result at 81% efficiency.

If you have a driver, an idea, I am listening  Thanks


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## 1215 (Aug 3, 2011)

Possibly meanwell ELN-30-12/15 or HLG-40-12/15 (12 if you want to overdrive to 3.3A) but you may need another XML in the circuit to make it happy with the HLG, however they are pretty nice build quality. Make sure to get the D or B models which have pwm/0-10v dimming (check product sheets for each model).


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## Mkala (Aug 16, 2011)

Thank you 1215 ! 

Looks interesting, I will learn more about these PSU


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