LED light engine manufacturers achieve greater lighting consistency

20 April 2015

With the LED transformation in full swing, there is another revolution for LED lamps – testing of colour values and brightness for improved lighting consistency.

The potential for output variations that seem to be inherent in LEDs can be problematic for lamp manufacturers, light fixture producers and customers who desire consistent colour and brightness. This may be especially true of customers who have dramatic architectural lighting installed, with LED fixtures that can travel continuously down hallways, around corners, and up stairways.

This “consistency revolution” is particularly concerned with the more complete testing of the performance of light engines, the power source of LED lamps. Containing one or more LED module and an LED driver, the variations in light engine output account for most of the variations in LED colour temperature, brightness and other output characteristics.

If LED light engines are not subjected to more comprehensive and consistent testing, it is likely that those output characteristics will continue to vary as current LEDs are replaced by rapidly changing technologies.

Controlling quality at the source

To alleviate this problem, many LED light engine manufacturers provide 100 per cent “functional testing” of lamps along with first article and periodic inspections of a production run. However, functional testing merely validates that the lamps will illuminate, and usually will not analyse the CCT (correlated light temperature), CRI (colour rendering index) or brightness of lamps. 

The more complete solution would be the comprehensive testing of 100 per cent of LED light engines, and those who manufacture those items are developing more sophisticated testing systems that will automatically and thoroughly test them before they are sold to lamp manufacturers.

Companies such as MADE (Manufacture and Design Electronics), are moving toward 100 per cent comprehensive testing, control, data reporting and recording. Also including production controls via a robotically-controlled test cell that will inspect and record the circuit boards for each light engine, including colour temperature, power, brightness and colour rendering index.

By testing and controlling those factors, light engine manufacturers will enable the production of LED lighting with much greater consistency in power, colour and brightness attributes, saving time and binning efforts in the process. MADE, for example, now applies this testing procedure to all types of customer LED light engine designs, including those for retrofit products such as the light strips that replace fluorescent lamps and ballasts.

An added benefit of this new approach is that production will be stopped if products are out of tolerance, thereby reducing the risk of scrapping them. Reducing such waste will enhance cost competitiveness and provide competitive advantages – both price and reliability – even with offshore suppliers.

The value of consistency

The consistency of LED colour attributes and brightness has a definite influence on lighting quality and applicability. 

It is noteworthy that even today’s more robust binning systems can fall short of providing the consistency that is promised by the 100 per cent light engine testing system. One reason is that the electroluminescence – the luminescence produced by voltage to an LED lamp – as well as colour of the light is determined by the lamp’s light engine microchip. Since the chips used in LEDs continue to change over time, their manufacturers often recommend a “blending” technique to achieve the desired lamp colour correctness and facilitate more accurate binning. However, this technique may not produce the consistent results that lighting manufacturers are looking for.

The new 100 per cent testing system can make adjustments during production runs in order to compensate for chip variations and achieve more uniform colour and brightness characteristics. 

Enabling accurate replacement

In conjunction with the 100 per cent inspection process, this new test system stores all pertinent LED light engine characteristics - from lot to lot - in a database that can be made accessible to lighting manufacturers.

This database could prove valuable to manufacturers for use in handling warranty claims and as an extended service to enable them to match the colour and brightness of an LED lamp from a given production lot years later when the lamp eventually requires replacement.

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