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A response to Projection Lighting and Xicato regarding Remote Phosphor Technology

Dr. Geoff Archenhold's right to reply...

In response to the letter received by Gary Heald, Projection Lighting and Roger Sexton, Xicato regarding the article in Mondo arc issue 47 discussing remote Phosphor technology:

Firstly, may I applaud Projection Lighting and Xicato for acknowledging and indeed supporting the need to be honest with end users and in particular Lighting Designers about the performance of LED Lighting fixtures when used in typical application operating conditions. The number of Lighting Designers I have spoken to in the past that have had bad experiences with LED products is frankly an embarrassment and burden the LED industry must put right in order to avoid an elongated adoption curve that still haunts CFL technology some 20 years after the technology was first introduced!

One comment would be that the information contained in the reader’s response does not appear to be in the datasheets available from their website. Therefore, how would an end-user know any of the following:

1. Are the efficacy figures quoted taken at 70C or 25C?
2. Are the total lumens quoted for the light module or for the whole fixture including optics?
3. Is the power rating quoting the real power or apparent power?

Each of these questions can yield significantly different lumens per watt answers and unfortunately this is a typical problem seen on many datasheets. Assuming the items in the reader’s response letter are correct, my advice would be to easily add these figures in a simple-to-use table enabling end-users to understand exactly the performance of the fixture in terms of cold and warm lumens for the light engine and total fixture with apparent and real power figures included. That way it is easier for end users to compare apples with apples.

If all sections of the supply chain agreed to adopt a voluntary performance measurement criteria to reflect the fixture performance an end user would obtain in typical applications then adoption would be much faster and good quality lighting products would very easily be differentiated from the bad. The ASSIST recommends website offers a similar type of guidance for a variety of applications.

For example, over a breakfast meeting at Lightfair a well respected CTO from one of the largest LED manufacturers said to me that the difficulty for the LED industry today is that the end user doesn’t know how to differentiate good products from bad anymore. We both commented that in the past it was relatively simple to look at a product and differentiate them because poor quality products had poor quality design. However, at Lightfair it became obvious that even the poor quality products are now so similar to the good products that the only way is to look inside them and undertake a full analysis. The question is how many end-users have the time, resources or knowledge to do this and the answer is very few or none!

For those in the general LED industry who would be willing to be part of a voluntary group to discuss this please contact me via the magazine and I will do my best to organise a meeting to discuss what can be done to take the responsible community of the LED industry forward to create an end-user focused performance benchmark.

Secondly, I have been called many things in my time but being conservative in estimating LED technology is a first! I have to thank Gary and Roger for this as, for the last six years, I have been told by so many people - from end-users to Government officials - that the contents of the mondo*arc articles are far too futuristic and products don’t live up to expectations, so to be pulled back by industry saying technology is here today is a new and bewildering experience!

On a more serious note, the articles are created to be informative and also as balanced as I can possibly make them given publicly available information. Some of the views are formed after discussions with senior people throughout LED lighting on particular trends or technologies and so are not just solely my own views. The Remote Phosphor Technology article was written after such a discussion with industry peers but as one would expect in this industry things move much more quickly than can be expected or predicted.

For example, in the latest edition of the mondo*arc LED column I cover the latest news from Lightfair with Philips winning an innovation prize for the Calculite downlighter which is also based on the Remote Phosphor Technique. Therefore, it does seem that many of my thoughts regarding potential barriers to market entry for this technology may have already been resolved by a variety of companies.

I do still hold my thoughts in the following respect:

• In the future, the industry may require variable CCT control and this is more complex to achieve with RPT technology, although not impossible with multi-part phosphors. Some companies such as Philips and PhotonStar LED are already bringing variable CCT products to market.

• Current standard LED downlights are very efficient so there is not much of a technology advantage at this stage for RPT in the market. For example, IST has a downlight that is above 65 lumens per watt efficient in application and that uses standard Philips Lumiled rebels.

• RPT based lighting still only represents a fraction of the total market volume and hence mass adoption is still to occur so the proof of volume production is still needed.

The production IP that has been developed by Xicato to create the phosphor plate seems to be a key step in producing reliable RPT based LED lighting fixtures and I look forward to seeing much more of the technology in applications near-term.

As I stated in my last article, viable LED products are already here but the question is how does the end-user pick the viable ones from those that are clearly not viable?


Geoff Archenhold


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