NIST team to develop new LED test method

Gaithersburg's NIST research team said that the temperature control heat sink makes the LED test method compatible with today's ordinary lighting. They are in the development of a new test process will help LED solid-state lighting industry. NIST Zong and Yoshi scientist Yuqin Ohno said, by providing a direct measurement and traditional measurement method is similar to that of the LED lamp brightness and color, the new method will help the manufacturer of LED lighting industry with close distance. Now, LED manufacturers and the lighting industry in the measurement method is diametrically opposed to the common method of the shortcomings of the semiconductor lighting is hindered the commercialization.

Graphic: this new test instrument, which can meet the needs of high-power LED manufacturers and the pan lighting industry, so that their data and the results of the comparison; the operator is from NIST Yuqin Zong. The main difficulty of LED emission is its working temperature, more specifically, the junction temperature in semiconductors. In order to ensure the rapid mass production of the device, the LED manufacturer uses a high-speed optical pulse to test to detect the color and brightness of the LED device. However, the 20ms pulse does not allow the chip to fully heat up to the "normal" junction temperature required for operation up to 60 C. Since the LED output is related to the temperature, the actual operating characteristics vary depending on the manufacturer's test conditions.

Unlike the LED manufacturers, the pan lighting industry tends to use a steady DC method to measure, and those LED chip users will like this way.

In 2008 Expert Symposium on Advances in Photometry and Colorimetry, Ohno and Zong mentioned in the paper, we developed a new method for practical measurement, any specific junction temperature of high power LED. "The new test method is based on a temperature controlled heat sink that uses it to adjust the LED chip to any junction temperature, which is better than the DC test LED output. These heat sinks are cheap and widely used, the team said, which is suitable for a variety of high power LED, including a series of LED arrays.

Up to now, Ohno and Zong have been applied to the 1W white light LED at 25 C in junction temperature, and the 20ms method is used to test the optical pulse.

After an initial effort to prove that using the new method and the test method of DC pulse used almost no difference what, now we are the next step of the experiment so that the DC method is more efficient, the early results showed that the use of the methods of testing, help eliminate LED and pan lighting industry gap. On this basis, solid state light sources must be able to optimize their thermal management systems and produce more efficient lamps.