While the speakers shared a positive outlook on LEDs in LCD TVs, they also expressed doubts about the viability of organic-LED) TV. Shin, Jacobs and Berkoff all believe that enhancements are coming so fast to LCD TVs that the OLED market will be stymied. Berkoff stated, "The best technologies don't always win."
While LEDs gain in the TV segment, they are already taking over in the notebook computer segment. Jacobs claims that the netbook market "is essentially 100-percent LED." He projects that next year, 93 percent of notebooks will use LED backlights. The energy efficiency is the compelling sell in battery-based systems, and LEDs enable thinner notebooks.
During an Advanced Lighting Summit, experts focused on reliability and energy efficiency. The reliability issue is multifaceted, but temperature control is paramount. Ann Reo, general manager of luminaire maker IO Lighting, noted, "Our fixtures look like heat sinks because they are."
Rico Schulz, technical director at Everlight Electronics addressed the useful life of LEDs in lighting applications, claiming that 50,000 hours is a good, conservative figure although some companies quote 100,000 hours. Schulz said, "It very much depends on the thermal management."
Thermal issues are key because LEDs don't radiate heat the way other bulbs do, and high junction temperatures can lead to lumen depreciation. Generally, once an LED looses 30 percent of its brightness (a level called L70 for 70 percent), it's considered to have failed.
Reo said the Energy Star program mandates 25,000 hours for residential LED lighting and 35,000 hours for commercial products. But Reo also claimed that some interior designers and architects want a five- year warranty. She claimed the key question for interior designers is "How do we change the light bulb." One answer is to discard the fixture.
Schulz said the industry needs to make advancements in two key areas. First he noted that increased efficiency is needed in the drive electronics. Current power supplies are around 80-percent efficient. "The next generation of power supplies will reach 90-percent plus," he said, stressing the need for a focus on longer product life.
Thermal issues are part of the problem, but there are reliability issues in the drive electronics as well as the LED components.
"Overall system reliability is only as good as its weakest link," Reo said. Schulz added that the low-cost electrolytic capacitors use in most power supplies will fail far sooner than the LEDs.
The takeaway is that LED-related markets are poised to grow rapidly. But the designs aren't simple, and electronic engineers need a new skill set to succeed with LED system designs in lighting.
Learn more about high-brightness LEDs in general, LED applications, and LED drive circuits at the EE Times LEDs and Lighting Virtual Conference. Scheduled for Wednesday (Oct 21), the all-day event features a keynote address entitled "The Transition to Solid State Lighting" along with a series of interactive panel discussions, virtual booths, and chat sessions with peers. An archive of the event will be available after Oct 21.
Maury Wright is conference co-chair for the EE Times LEDs and Lighting Virtual Conference