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Issue 62 Aug / Sep 2011

LED modules seem to be all the rage but how do they perform, are they useful and what will the future hold? Our LED Expert, Dr Geoff Archenhold, puts the big four front runners to the test - with help from the Lighting Association Lab.

What we asked for...

Due to the vast number of LED module variants available it was decided to evaluate a small subset based on a light engine output of 1000 lumens with a Warm White (3000K) colour temperature.

• The overall efficiency figures included driver and thermal losses but excluded any optical losses due to reflectors, diffusers etc.

• All measurements were taken when the modules were deemed at steady state (ie; after they had warmed up and small lumen output deviation was observed).

• The modules were tested as supplied by the manufacturer along with recommended heatsink and control gear.

• The cost of each module is based on a ‘guide price’ for a one-off order of 1000 modules in isolation. This was done to determine a price:performance ratio which is one of the most important factors required by the end-user market today considering the austerity budgets of most companies. Cree’s sample was the only module that included a built-in power supply.

• All of the modules appeared to be manufactured to a high standard.

• Only one module sample was tested from each manufacturer so caution has to be undertaken when interpreting the results.

• No lifetime data was obtained on the modules and therefore it was not possible to define lumen maintenance or other lifetime characteristics.

• See table B below for detailed module test result figures.



68.95 LM/W

79.3 LM/W
67.36 LM/W
86 LM/W
RA: 81.5 RA: 78.8 RA: 81.1 RA: 92.3
R9: 22 R9: 4.6 R9: 14.3 R9: 91.8
CCT: 2941 CCT: 3070 CCT: 3076 CCT: 3137
COST: $39
(not inc heatsink/driver)
COST: $93
(not inc heatsink/driver)
(power supply integrated)
LM PER $: 30 LM PER $: 13 LM PER $: N/S LM PER $: 20


TABLE B: MODULE TEST RESULTS IN DETAIL (click to open larger version)

GRAPH A: POWER SPECTRAL DENSITIES (click to open larger version)

What we came up with...

It is clear that at the 1000 lumen warm white (3000K) lighting criteria, all of the LED modules exceed 65 lm/W which is highly impressive and demonstrates the rate of progress made in just a couple of years. The modules were tested without secondary optics which would of course reduce the luminaire efficacy. However, this enables a truer comparison of the modules.

Interestingly, the LED modules achieve the efficacy performance in a variety of different methods, whether it is using integrated or external ballasts, standard or remote phosphor LEDs and even combinations of different coloured LEDs. This variety of module demonstrates that the module market is still embryonic and companies are still investigating what methods and technologies will provide the best overall performance, production yield and costs.

It is difficult to draw any firm conclusions from such a small sample test of each module especially as it is not possible to determine if the modules supported are standard production modules or near production high specification versions. However, it is clear that the Cree LMR4 module offers leading efficacy performance with a high CRI value due to the TrueWhite technology (it is important to note the efficacy test performance is substantially higher than the products’ datasheet which is unusual). The technique of using two or more LED colours is well known in the entertainment lighting industry. However, it seems that the Cree TrueWhite system is a good approach for high CRI modules.

One area of disadvantage for type 1 LED modules is that electronic ballasts or drivers are the most unreliable part of an LED system and therefore lifetime aspects may be an issue for the Cree LMR4 products. The external electronic ballasts/drivers for type 2 modules can be replaced easily without the need to recycle the product.

At a recent US Department of Environment industry event looking at LED fixture reliability, interesting data from Appalachian Lighting Systems (Ellwood City, PA) was presented on the cause of 29 field failures from 5400 outdoor luminaires where the driver (power supply) caused 52% of the failures; the luminaire housing caused 31%; LED packaging caused 10% and the driver controls caused 7%. Therefore, over 59% of failures seen were to do with the LED driver and controls used within the SSL system!

The big challenge for the LED fixture manufacturers are which modules should they base their new LED luminaires on as there is a significant choice of formats, sizes and options. From the units supplied by the manufacturers the majority of LED modules are still not compatible / interchangeable with each other and therefore product designers will still have to design around specific modules.

One advantage for system designers is most of the modules provided in the test come with a variety of secondary optics options to allow optical beam control for many types of applications. This can save considerable time for a luminaire designer if complementary optics or reflectors have already been designed for the LED modules allowing systems to be placed in the market rapidly.

One of the major aspects the luminaire manufacturers will need to consider in the near future will be the challenge that standard LED modules will bring to the market. For example, will standard light engines degrade the individuality or design innovation of the fixture manufacturer? If a user is presented with five lighting fixtures, all having the same LED modules incorporated, where is the product differential?

My thoughts are that a purchaser would look to differentiate products based solely on price as there should not be a technical difference between units with similar modules. Of course the lighting industry is not purely based on cost but also reputation, brand value and quality of service. However, losing a technology differentiation tool may mean higher quality fixture manufacturers may struggle.

It may be that LED modules are a short term phenomenon for lighting manufacturers to leverage products rapidly into the lighting market. However, in the mid-to-long term they will wish to develop their own light engines to enable them to differentiate themselves. In a couple of years from now the thermal challenges currently seen with LED lighting will be significantly reduced as LED efficiencies will have increased to such a high level whilst new electronic skills will have entered into the traditional lighting fixture manufacturers enabling them to be self sufficient.  

Whatever the thought process there certainly is a variety of LED modules available today and if Zharga is successful in the future most will be interchangeable with each other enabling better light engine choice and hopefully a more competitively priced market.

It is important to state that there is currently no long term lifetime data of LED modules and I believe this is going to become the next area of focus for the LED industry. However, it is not as simple as just looking at lumen maintenance data as was shown in typical field data where the LED drivers represented more than 50% of LED system failures.

What will be interesting to study, once these modules are adopted by lighting luminaire manufacturers, is how they perform in actual lighting fixtures. Watch this space for further tests of fixtures and different lumen category modules.

Geoff Archenhold has been seconded twice to the UK Government to support the Lighting, LED and Photonics industry and currently helps LED companies develop business plans to raise investment from the finance community. He is an active investor in LED driver and fixture manufacturers and a lighting energy consultancy. The views expressed in this article are entirely those of Geoff Archenhold and not necessarily those of mondo*arc.

LINKED ARTICLE: Identity Crisis
The shapes, formats and types of LED modules submitted to the bench test by the leading manufacturers demonstrate how much choice there is for lighting manufacturers to consider and evaluate when starting a new product development.



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