Searching the most efficiant warm white LED chip

[Mkala]

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

 

[John_Galt]

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

 

[Mkala]

Thank for your reply John

Took from datasheet :

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

Vf@350mA = 3V
P@350mA = 3V * 0.35A = 1.05W

Vf@700mA = 3.2V
P@700mA = 3.2V * 0.70A = 2.24W
Lumen @ 700mA = ~185% of LM@350mA

Vf@1000mA = 3.3V
P@1000mA = 3.3V * 1.00A = 3.3W
Lumen @ 1000mA = 250% of LM@350mA

Efficiency :

BIN    LM@350mA   LM/W@350mA LM/W@700mA LM/W@1000mA
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

 

[csshih]

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?

 

[Mkala]

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 ?

 

[deadrx7conv]

Read thru the fixed lighting forum.

 

[WeLight]

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

 

[-Gast-]

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

But i cant measure cri here....

 

[jason 77]

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

 

[deadrx7conv]

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

 

[blasterman]

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.

 

[RedmEx]

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

 

[deadrx7conv]

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.

 

[blasterman]

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.

 

[Th232]

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.

 

[Mkala]

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.

 

[Mkala]

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

 

[Mkala]

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

 

[Oznog]

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".

 

[zzonbi]

"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?