GaN transistors promise more light for less energy
Focusing their attention on voltage transformers featuring GaN transistors, the researchers have run a series of practical tests that show the drivers developed using this new semiconductor material were extremely robust.
Incandescent light bulbs are now banned in the EU but energy-saving lamps are still far from popular with some customers. In 2016 halogen bulbs over 10 W will also be banned and LEDs will become the light source of the future.
LED retrofit lamps for use in standard bulb fittings are predicted to replace traditional energy-saving bulbs for the first time from 2015. By 2020 it is forecast that LEDs will have captured between 88 and 90 percent of the lighting market.
However, LEDs do have weaknesses and can be sensitive to variations and spikes in power. To function properly, they need a driver that ensures a constant supply of power at all times. The driver can have an impact on light yields and lifetimes of the LED lamp as a whole.
“Heat plays a role both in the brightness and the service life of LED lamps,” explained Dr. Michael Kunzer, group manager at Fraunhofer IAF.
Gallium nitride transistors are able to switch at high frequencies and the switching speed can have a significant impact on the size of the coils and condensers built into the drivers for energy storage. In a GaN-based driver, the switch speed can be made as much as a factor of 10 faster than that of its silicon equivalent.
“Applied to a smaller surface, this means it is possible to make switching cheaper. The whole LED lamp can be made lighter and more compact while delivering the same or even improved illumination,” explained Kunzer.
Since the energy storage component plays a decisive role in manufacturing costs, this could have a positive effect on the price of the finished product.
Kunzer and his team have been able to boost the efficiency of the GaN driver to 86 percent which is between one and four percentage points better than its silicon equivalent.
When compared with the silicon transistor LED lamps available on the market, the scientists were able to increase the light output: while the luminous flux of commercial LED retrofit lamps featuring silicon components is around 1000 lumen, researchers from the IAF have been successful in increasing this to 2090 lumen.
“20 percent of energy consumption worldwide can be attributed to lighting, so it is an area where savings are particularly worthwhile. One shouldn’t underestimate the role played by the efficiency of LED drivers, as this is key to saving energy. In principle, the higher the light yield and efficiency, the lower energy consumption,” said Kunzer.
The researchers plan to showcase a demonstrator of their retrofit LED from April 7-11 at the Hannover Messe in Hall 2, Booth D18.
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