The latest LEDs can reliably operate at drive currents well above binning currents, delivering more lumens and robust luminaire life while lowering system cost, explain David Cox, Don Hirsh, and Michael McClintic.

In the evolution of the microprocessor there have always been uses for faster, more powerful or more compact processors. Historically, with each new generation of microprocessors, electronic devices would in turn become more sophisticated, smaller, faster, and/or cheaper. LED efficacy has been improving similarly to the evolution of the microprocessor, but LED-based illumination designs are not consistently taking advantage of capabilities such as brighter operation at higher drive currents. Today, luminaire manufacturers may find that the surest path to lower system cost is to take advantage of the full LED operating capacity or lumen output that they are already paying for while relying on the growing statistical evidence that they can do so and deliver long product life.

Table 1Advances in the production of lighting class, high power LEDs should cause the lighting industry to reassess how to create cost-optimal, LED-based designs. Several advanced LED manufacturers, Cree included, have developed a large and expanding body of information concerning performance maintenance of LEDs over time and temperature. This knowledge of long-term behavior is now standardized in LM-80 data sets that track lumen maintenance and color shift and in TM-21 projections of that performance over longer time periods. See for details on TM-21 methodology.

For Cree, the data shows, in the highest quality parts and in well-designed systems, that LEDs can operate at high current and high temperature levels with fewer performance penalties than ever before. This same data calls into question legacy luminaire and driver design methodology that has yielded systems that drive the LEDs around binning-current levels rather than over a wide range of drive currents and temperatures.

Using LEDs at higher operating capacity can deliver more lumens per LED with a corresponding reduction in system cost. For many lighting applications, more aggressively priced products can be created with reduced component count. Such a design methodology can result in higher operating temperatures and lower efficacy. Still, taking full advantage of an LED’s operating capacity becomes an attractive option for applications requiring maximum lumen output at a reduced cost.

Unused Operating Capacity
Reliability Data & Projections
Color Shift Data
Analyzing Tradeoffs
System Constraints

Generally, however, LEDs have far more luminous capacity than most designers are using. The highest quality LEDs are capable of operating at sustained, elevated currents and temperatures far above manufacturers’ binning information. New luminaire and lamp designs should take advantage of these attributes. For lighting class LEDs, there is no reliability penalty for using more of this capacity.

Orginal Source “Leds Magazine” View here.