Advanced LED Drives Detailed at Darnell’s DC Building Power Asia

December 12, 2011 by Jeff Shepard

Speakers from Taiwan’s Industrial Technology Research Institute (ITRI) and Germany’s Osram AG described new LED drive approaches this week during Darnell’s DC Building Power Asia in Taipei. The new drives were designed to optimize solid-state lighting (SSL) performance and reduce cost in buildings with dc power distribution architectures. In both cases, 380/400Vdc power distribution was identified as an optimal power source.

During the plenary session, Dr. Chi-Chun Huang, Researcher with ITRI discussed "LED Lighting, Now and Future." Because the cost of LED lighting is a key factor slowing the adoption of this technology, Dr. Huang identified high-voltage dc power as a key way to reduce the cost of the three highest-cost elements in an LED lighting system; the LEDs, the heat sink and the driver.

He identified a cost-effective solution using a compact LED light-engine in which the dc-dc driver IC and LED chips are bonded on the same substrate. Operation directly from 380Vdc input power reduces the number of components in the driver circuit substantially lowering the cost. In addition, by using the latest high-voltage LEDs, a higher operating efficiency can be achieved, reducing heat generation, and lowering the cost of the needed heat sink.

The following morning, Michele Menegazzi from Osram described a novel linear driver approach for LEDs. While the efficiency of the linear driver is lower than a corresponding switch-mode driver, the linear driver can still achieve 85% or greater efficiency, if the input dc power bus is relatively stable. While the proposed solution is less efficient compared with switching drivers, it is more efficient compared with other common lighting technologies such as CFLs.

With a well-regulated dc power bus, the efficiency is 10% lower compared with a switch-mode solution and the cost is over 60% lower, dramatically reducing the overall cost of the luminaries. The elimination of the need for an EMI filter is one of the key factors in the lower cost of the linear solution. Operation of LEDs from 230Vac, 48Vdc and 400Vdc was analyzed and the highest cost-to-performance ratio was achieved with a 400Vdc power source.

Mr. Menegazzi concluded that the best energy saving performance with SSL could be reached under the following conditions: DC power grid with small voltage tolerances and voltages up to 400V and smart grid systems with sensors (ambient light, occupancy, and so on) to optimize required flux. When combined with an optimized linear driver, this approach can also provide reduced costs compared with other alternatives and accelerate the adoption of solid-state lighting.

More news and information regarding the latest developments in Smart Grid electronics can be found at Darnell’s SmartGridElectronics.Net.