I recently got to speak with Tom Griffiths, senior marketing manager, color and spectral sensing, of sensor driven lighting at AMS AG, about the company’s approach to creating tunable white light.
Tom pointed out that while everybody wants to deliver lighting performance that is right on target, the need for binning results from the manufacturing reality that the performance of fabricated LEDs inherently varies. Also, he noted that in the fast moving LED lighting industry, LED lighting manufacturers tend to switch to newly improved LEDs every six months to a year to take advantage of the latest enhancements in metrics such as light output, efficiency, longevity, as well as reduced cost.
Three Ways to Achieve Tunable White Light
Tom said there are essentially three ways to achieve tunable white light. The first, and least accurate way of tuning white light is to just guess and combine a warm LED string and a cool LED string, and hope for the best.
Another way is using a microprocessor with built-in intelligence that adjusts the warm and cool LEDs. This second way will use the microprocessor to examine LM-80 data and use that data to look up TM-21 tables to show what exact power input at that color temperature, produces that exact light output. This is a costly method because the data and lookup tables have to change for each new LED used. Also, integrating a microprocessor is an added expense.
“The only way to get away from that is to get a sensor in there,” Tom said. The AMS approach uses sensor technology and a feedback loop to adjust the light output and color temperature.
This sensor approach can allow the use a wider variety of LEDs. The binning of an LED makes up to about 25 percent of the cost according to some estimates. So, using the AMS sensing and management technology could somewhat reduce the cost of the LEDs because the binning does not have to be quite as tight. Reducing the price of the LEDs required is only one part of the potential cost savings.
Human Eyes are Very Good At Seeing Tiny Differences in Brightness
“Very very small differences can make a visible difference in the lights,” Tom Stated. He said that the human eye can detect deferences in brightness of as little as two-tenths of one percent.
He pointed out that while LED prices continue to plummet, savings on LEDs don’t matter as much as making it a tunable system. In fact, in recent years, Tom said that power systems are becoming the more costly component, especially in smaller systems.
According to Tom, the AMS system allows manufacturers to not only tune the white light of particular LEDs, but it also gives the producers the flexibility to switch to using different LEDs with no or only small changes in system design.