Have a Lighting Question?  Ask the Expert!

Jim,

Thank you for using CREE!

To keep your design simple and maximize Battery run time I would choose option C.

To reduce your system losses - do not use the Spring type battery holders - they have very high resistance.. use either blade holer or flying leads..

Good Luck and let me know how your design turns out

Muhammad,

Congratulations on INDIA winning the Cricket World Cup!

Cree would love to help you succeed in your efforts to develop Solid State Lighting in INDIA.

We have posted a lot of our knowledge base on Cree's landing page on Element14 (see link below)

http://www.element14.com/community/community/suppliers/cree

Check out the Application notes, Reference designs and Tools Section

From a system design stand point, check out Cree's online System design tool: Product Characterization Tool (PCT)

http://pct.cree.com/Register.asp

This tool allows you to enter you System Design requirements (System Lumens, Optical Efficiency, Electrical Efficiency)

then helps you evaluate the right LED drive current to optimize your design.

For all valid LED drive currents, the PCT quickly and easily does the following:

• Shows all critical LED design parameters, such as luminous flux and efficacy, for selected LED models
  
• Performs de-rating calculations based on junction temperature (Tj)
  
• Calculates LED valuations, such as lumens per dollar (lm/$)
  
• Estimates simple LED design parameters, such as the number of LEDs required and total power consumption
  

The PCT uses specifications and characteristics from LED data sheets to accurately compare LED parameters with changes in flux, price and junction temperature. The PCT can compare up to three LED models side-by-side to aid in making critical design choices.

To get to market fast you may want to look at Cree's more integrated Lighting modules and LED Array products like the LMR4, LMR2 (coming soon), MPL, CXA20

Cree also works with complimentary suppliers and system design experts to help you get to market faster..

Understanding what problem you are trying to solve is one of the most important starting places..  How much light is need in your application

Cree published a very good application note which documents the design process the system..

here is the link..

http://www.cree.com/products/pdf/LED_Luminaire_Design_Guide.pdf

Hopefully this is a good starting point on your journey to changing the lighting world in INDIA!

CHEERS!

David Cox

Thank you for the great question!

Delta CCT = the Change in CCT over angle – (CCT = correlated color temperature)

http://en.wikipedia.org/wiki/Correlated_color_temperature#Correlated_color_temperature

when we talk about delta CCT we are usually talking about the how much the color of the white light changes over the viewing angle of the LED (smaller is better ). This is critical for some applications like linear lighting and a don’t care for outdoor lighting

Alla,

thank you for the question:

From the element14 webinar I gave on March 29th 2011 slide 18 titled LED Chips: Size Doesn't Matter

I show power die from Cree's ETC and EZ chip families that range from 0.35x0.47mm to 1.4x1.4MM in size

The link to the on-demand presentation is here: https://newark.webex.com/newark/lsr.php?AT=pb&SP=EC&rID=49322112&rKey=23487de9a1e644c9

from Cree's small chip family the chip size is 200x200μm

hope this answers your question

What are the chances that CREE will start putting more information in their datasheets, or at least offer some guidance on what the datasheets don't say?

Take the X-Lamp XR-E for example. Any absolute maximum ratings? no just Characteristics, any recommended operating conditions? no just characteristics.

Characteristic maximum current 1A (> 5000K white), 0.7A (others). DC pulse characteristic 1.8A, 1kHz, 10% (all). What about other frequencies and duty cycles? What about pulse ratings for photo-flash type applications? What about current ripple ratings at 10s or 100s of kHz as typically produced by switchmode drivers? What about guidance on the consequences of over/under driving? You don't need 50,000 hours life from a photo-flash for example.

You make the things, you must know a lot about them but seem to leave your customers guessing.

you are luck!

I happen to have lots of experience with power -

Inverter  takes DC and makes AC - so for CFL and EL products you need to have AC signal - many people call the products that convert the power from DC to AC drivers or inverters ..

if you want to use the most efficient light source you will need to use LED technology - which will require a different kind of driver - dc/dc constant current driver-

Element 14 has many suppliers that you can help wih your power requirements

Good luck on your project

You are in Luck - Cree Agrees with you - We are trying to make it easier to adopt Solid State Lighting..

if you look at the latest Cree Data sheet for the

Cree® XLamp® XM-L EasyWhite™ LEDs

http://www.cree.com/products/pdf/XLampXM-L_EZW.pdf

Cree choose to bin this part close to the target application operating conditions (MR16 20W LED replacement)

•Binned at 85°C with single EasyWhite bin per CCT

customers no longer have to guess or do math to figure out what LED CCT and Flux at 85C Tj

we even added a chart labeled "RELATIVE CHROMATICITY VERSUS CURRENT AND TEMPERATURE (CRI 80)"

to help customers understrand how their design will function in Pulsed Over-Current above the max rating:

Pulsed Over-Current Driving of XLamp LEDs: Information and Cautions

http://www.cree.com/products/pdf/XLamp-Pulsed-Current.pdf

Please give us feedback on what you need to help you solve your lighting problems