Cree launches TEMPO luminaire testing program

Sept. 28, 2011
Aimed at Cree’s LED component customers, the TEMPO luminaire testing and evaluation program includes 21 key test points across thermal, electrical, mechanical, photometric, and optical design elements.
One recurring obstacle to broad deployment of solid-state lighting (SSL) is the complexity of developing reliable LED-based lighting systems, and Cree plans to help its LED component customers with its new TEMPO (Thermal Electrical Mechanical Photmetric Optical) luminaire testing and evaluation program. Luminaire designers can utilize Cree services to validate a design before joining what's become a queue at LM-79 testing labs.

TEMPO is essentially a sequence of services that Cree LED customers can access throughout the design cycle of integral lamps or luminaires. For example, Cree will help with optical and thermal simulations early in the design process. Later in the process Cree offers what it calls SPOT (Single Point Of Test) testing on a light engine. And then the TEMPO-21 test, covering 21 test points, will be performed on complete luminaire or lamp designs.

A table from the TEMPO-21 Executive Summary page. At the conclusion of the TEMPO-21 tests Cree will deliver a sizeable document to the customer who can then share that data with its customers, providing a third-party validation of performance. Table 1 is taken from the Executive Summary of a sample TEMPO-21 test that Cree performed on one of its reference designs. That table is focused primarily on optical and photometric properties and power consumption, but the full document addresses the other design elements as well.

According to Mark McClear, global director of applications engineering at Cree, the TEMPO concept evolved from bad design practices in the field that often lead to luminaire makers blaming the component supplier. McClear used an example where a customer chose improper glue that created gases as temperature increased inside the luminaire, damaging the LEDs.

McClear said that luminaire makers have no-one to turn to for help and often approach LM-79 and Energy Star testing not knowing if their design will pass. There are specialty firms that might evaluate a thermal design for a substantial fee. LM-79 testing cost $1000 or more, and manufacturers often must wait for a test slot.

Measurements are made on a 2-in grid. Some of the other tests that TEMPO-21 includes in the electrical area are driver efficiency, transient analysis, dimmer compatibility, power analysis, and Hi-pot testing for dielectric breakdown. In the thermal and mechanical area, the tests include validation of a proper solder point for junction-temperature monitoring, thermal imaging with an infrared camera, and a chemical compatibility analysis. The test also includes a TM-21-based estimate of product lifetime that accounts for the thermal design of the fixture, and a review against Energy Star criteria.

Ultimately TEMPO-21 is both a superset and subset of LM-79 which McClear says covers only about half of the evaluation points that are critical to judge a design. But Cree can't perform the complete LM-79 test suite right now. Expect that to change, however, as the company is planning to install a moving-mirror Type C goniophotometer that is required for some LM-79 tests.

That leads to the question of whether Cree will seek official recognition as a Certification Body so that it could handle LM-79 and Energy Star testing for its customers. However, McClear said the company has no such plans for now.

Cree believes it can offer the TEMPO services with turnaround times in days rather than weeks and help customers accelerate time to market. SPOT tests will cost only $300 and a full TEMPO-21 test will cost $1200. The company is clearly not looking to profit directly from the services at those price levels, but rather TEMPO is simply another way to achieve Cree's stated mission of accelerating the adoption of LED lighting.

Although TEMPO was formally introduced in late September, the company has already performed a number of TEMPO-21 tests for customers. When asked if he knew of any similar program at other LED vendors, McClear said, "I think this is something the other component vendors should consider doing."