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Driver Creates Short, Powerful Pulses with LEDs

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Providing high-brightness, rapidly pulsed, multicolor light, a novel LED driver could displace more expensive lasers and other light sources in scientific, industrial and commercial uses.

Researchers at Sandia National Laboratories have already used it in imaging studies aimed at creating cleaner, more efficient engines that could help improve local air quality and public health and reduce the impacts of climate change.

Designed by Sandia electronics engineer Chris Carlen, the LED Pulser drives high-power LEDs to generate light pulses with shorter duration, higher repetition rates and higher intensity than is possible with commercial off-the-shelf LED drivers.

The device has achieved pulse durations in the tens of nanoseconds. A single device can emit up to four different colors, each with independent pulse timing, from nearly the same area.

"It was more of a curiosity initially, but then something came up where a light source being used in a lab wasn't working out, so I decided to try to make a quick prototype to pulse an LED, which worked out pretty well," Carlen said.

The LED Pulser can be used in a variety of technical applications that normally demand far more expensive laser or arc lamp sources and optics.

light pulses with shorter duration
Sandia National Laboratories engineer Chris Carlen demonstrates the LED Pulser, which generates light pulses with shorter duration, higher repetition rates and higher intensity than off-the-shelf LED drivers. Courtesy of Dino Vournas/Sandia.

In one study, it delivered 50-ns pulses at 200 kHz that "froze" the motion of liquid droplets. This strobe effect allowed researchers to capture high-resolution images of atomization in a high-pressure diesel fuel spray. Spray atomization and mixing profoundly affects combustion in spark-ignition and diesel engines.

The LED Pulser also was used to image the evolution of diesel soot concentrations, providing information needed to predict soot formation and oxidation processes. Timed to match the camera exposure duration of 2 μs, and with strong pulse intensity relative to combustion-generated light, the device allowed full-field imaging at high frame rates.

Since the LED Pulser is designed to deliver as much power as possible, the circuits can drive the LEDs to the brink of destruction. A commercial version of the device would require an improved design to achieve low failure rates even at high power, or lower power to achieve an acceptable failure rate.

Carlen is working on a LED Pulser that is 10 cubic inches in size and can produce 240 A of drive current, for about 150 W of peak optical power, depending on the LED used. He is also trying to build a faster driver circuit.

"What's interesting about the Pulser is the power density, i.e., how much power it can deliver compared to its size," he said.

Photonics Spectra
Dec 2015
camerasResearch & TechnologyAmericasCaliforniaChris Carlenlight sourcesLEDsdriverLED PulserimagingTech Pulse

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