newsletter link
mondo arc


Issue 64 Dec / Jan 2011/2

Following our benchtest of 1000lm LED modules in issue 62, our LED expert Dr Geoff Archenhold tests high power 2000lm modules to see if they exceed CFL equivalents in common downlighter applications.

As LEDs are now firmly challenging CFL based downlighters, the latest LED modules were tested at 4000K and with a lumen output of 2000 lumens. The CCT and lumen output were chosen as a common metric for 2x18W and 2x36W CFL equivalents. Before I get complaints I would suggest that 2000 lumens is slightly less than a 2x26W CFL equivalent but the light output ratio of LED based downlighters are significantly higher than their CFL equivalents so the tests should be treated as an approximation. Nevertheless, the absolute results demonstrate what will be possible now and in the future.

Test Method for Measuring the lumen output and CCT/CRI values
There were two main categories of photometric testing undertaken for each light module including:
1) Lumen Output
2) Spectral Power Distribution – CCT and CRI

The Lumen Output was determined for each light module by placing it ‘cap-up’ at the top of a 1.8 metre Integrating Sphere. A correction factor for each sample was taken in order to make allowances for the absorption of inter-reflected light within the sphere. The correction factor is determined by the use of a calibrated and known auxiliary lamp mounted behind a baffle within the sphere.

Each light module sample was then switched on and allowed to stabilise. In our tests a light module was deemed to be stable when the variation of at least three readings of the light output (Lumens) over a 30 minute period, taken 15 minutes apart, is less than 0.5% of the total light output from the module. Each light module sample was operated using a stabilised power supply at 230V (±1V). The lumen output of the sample was monitored (observed using software graph display) and a lumen output reading was recorded every minute until stable. The stabilised lumen output is calculated from the average of three readings recorded 15 minutes apart during the stable 30 minute period.

The spectral power distribution (SPD) measurements are required to accurately derive the Correlated Colour Temperature (CCT) and Colour Rendering Index (CRI) for all of the light modules. In order to measure the SPD of each sample they were then measured using a spectroradiometer (a spectral correction factor was measured prior to lumen output measurements using an auxiliary lamp in the same way in order to provide a traceable calibration reference point).

Following this, three spectral scans (with a wavelength step size of 2nm) were taken for each light module. Using dedicated software, the spectral data for the three scans were then averaged and used to determine the Chromaticity Co-ordinates, CCT and CRI (Ra) of each sample.


POWER SPECTRAL DENSITIES (click to open larger version)


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


RA: 83
R9: 11
CCT: 3969

The Osram module is based upon the new PrevaLED Core C –Z2 3000 lumen module that delivered 2426 lumens with system power consumption of 28.3W to provide a system efficacy of 85.8 lm/W. The PrevaLED utilises a Chip on Board (COB) design to improve the light output homogeneity which could reduce the need for diffusers.
The LED light engine starts with initial SCDM of 4 which is quite high in terms of most LED binning systems. However, with a CCT of 3968K and a CRI of 83 and R9 value of 11.1, the module meets most of the colour quality requirements for a downlight application. The use of a high efficacy COB LED array enables a high efficacy system without the need for active cooling or significant numbers of LED emitters and therefore the system costs should be competitive for such solutions in practice.


XICATO XSM 8040-2000/C4A
RA: 81
R9: 15
CCT: 4018

The Xicato XSM 8040-2000/C4A LED module provided a module efficacy 51.8 lm/W and consumed more than 46.1W of system power. The efficacy was significantly lower than the rest of the modules and even at Time=0s the efficacy was 53.32 lm/W. However, further inspection of the system showed that the heatsink supplied exposed the rear of the module which is poor thermal management practice and the heatsink is not making good thermal contact to the module as shown below.
The driver used with the Xicato module also had a very poor PFC of just 0.51 so it would be advisable to use an LED with active PFC in order to meet market criteria of PFC > 0.9. The Xicato module uses remote/cold phosphor technology based LED module producing 2386 lumens with a CRI of 81.1 and an R9 value of 14.6. The advantage of Xicato modules are such that the colour consistency between modules is very high and these modules are stated to have tolerances less than 2 standard McAdams ellipses.


RA: 83
R9: 25
CCT: 3993

The GE Infusion LED module delivered over 2439 lumens with a CCT of 3993K, a CRI of 83.1 with an R9 value of 25.1. The total module efficacy was determined to be 70.3 lm/W. The Infusion module is small and with a simple twist and lock, the light module can be easily removed and replaced and no additional hardware is necessary.
The GE module appears to utilise the Cree XPG LEDs as can be seen from the 14 white LEDs below. The Infusion LED solution maintains incredibly consistent colour quality from module to module (as low as 2-MacAdam ellipse consistency). The modules are also available in
80 or 90 CRI options although the available lumens will change accordingly. The modules are available with a range of reflectors, optics, drivers and dimming controls to allow fixture manufacturers to rapidly build fixture designs that can be updated in the future.


RA: 85
R9: 26
CCT: 3855

The Philips Fortimo module utilises sixteen individual Luxeon A LEDs driven with a 1000mA driver and was second in terms of luminous efficacy coming in at 87 lm/W with 2365 lumens consuming 27.1W of power.  The Fortimo seems to operate with eight LEDs in series and two banks of LEDs in parallel so the LEDs are run at 500mA. The Fortimo module had a good CRI value of 84.8 and an R9 value of 25.8.
The Fortimo module utilises active cooling technology with a Sunon long-life ball bearing 0.28W fan attached to the rear of the heatsink to improve the efficacy and lumen maintenance of the module. There are no problems with using active cooling technologies, however their use will be restricted by environmental aspects such as airflow suitability, cleanliness of the environment such as dirt/dust and most importantly noise acceptance.


RA: 92
R9: 56
CCT: 4039

Individual LEDs within the module are tested and matched in order to meet the designed chromaticity specification by mixing the proportion of intensity from the 14 red and 24 white/blue LEDs incorporated into the light module as shown below. In order to achieve the CCT and CRI combination, Cree has utilised different white/blue bins on two LEDs (G5 and G11) but with such a large number of LEDs (36 in total) within the light engine one could argue this solution would be significantly more in cost to other modules tested and also explains the higher efficacy figures as the LEDs will not be driven as hard as other modules.
The power spectral density of the Cree module is drastically different from the other LED module PSDs due to the inclusion of the two different white/blue and red LEDs. Interestingly, the R9 value isn’t that high at 56.1 so colour rendering may not be as good as high CRI phosphor based LEDs with a wider more continuous PSD.



The modules all achieved greater than 70 lm/W (except for Xicato which always scores highly on colour consistency), offered CRI >80 and delivered more than 2300 hot lumens making them ideal solutions for replacing 2x26W CFL based downlights. Obviously, the results are based on the LED light engines by themselves and in order to be of use secondary optics need to be employed in order to deliver the light on task which will reduce the efficacy and lumen output figures.

Interestingly, the LED modules achieve the efficacy performance in a variety of different methods from remote phosphor based systems, through arrays of individual emitters (single and multiple colours) to single chip on board LED arrays.

In terms of cost effectiveness, one would suggest in the absence of pricing information from manufacturers, the COB solution from Osram would offer the best price performance ratio as it uses less packaging materials and provides high efficacy than multiple LED arrays.

Again, as in the first module test, the variety of LED modules demonstrates the market is still embryonic and companies are still investigating what methods and technologies will provide the best overall performance, production yield and costs.

Special thanks go to Steve Poole and Paul Gilmartin of The Lighting Association Laboraties who carried out the tests. The bench tests were carried out at The Lighting Association Lab using LM-79 test protocol. A UKAS accredited laboratory located within the UK, LA Lab is also able to provide international CB test and certification in association with their certification body TUV Rhienland. It is a UK Government appointed Notified Body under the Low Voltage Directive.




Philips Fortimo SLM Gen 2

  • Cree LMH6

  • GE Infusion

  • OSRAM PrevaLED Core

  • Xicato XSM 8040-2000/C4A

Related Articles


Follow us on…

Follow Mondo Arc Magazine on Twitter Follow Mondo Arc Magazine on Facebook Follow Mondo Arc Magazine on Linked In

mondo arc india

darc awards DWLF IALD PLDC LRO