by Peter Demchenko @ edn.com:
Low-current switching regulator ICs often use a Darlington as the output switch. The power conversion efficiency in this case can be improved with the help of only two cheap components. To make this possible, the chip should have a separate pin for the collector of the driver transistor Q1 (Figure 1). At startup, D1 forms a path for the collector current of Q1. Later, D1 and C1 comprise a current-additive rectifier which enhances the collector voltage and current of Q1, hence reducing voltage drop on the closed switch Q2.
Improve efficiency of low-cost switcher – [Link]
Research at Lawrence Berkeley National Laboratory (Berkeley Lab) has led to solar cells with record-breaking efficiency. Contrary to conventional scientific wisdom, it turns out that efficient solar cell materials are characterised by high photon emission instead of high photon absorption.
According to the researchers, external fluorescence is the key to approaching the theoretical maximum efficiency for conversion of sunlight into electricity. The maximum efficiency, called the Shockley-Queisser (S-Q) efficiency limit, is approximately 33.5% for a single p-n junction. An analysis by a member of the research team indicated that gallium arsenide is capable of approaching the SQ limit. Based on this work, Alta Devices Inc., a private company spun off by the researchers, has fabricate gallium arsenide solar cells that achieved a record conversion efficiency of 28.4%. [via]
Researchers find key to better solar cell efficiency – [Link]
Materials science and engineering researchers at the University of Toronto have developed the world’s most efficient organic light emitting diodes (OLEDs) on plastic. This paves the way for a flexible form factor as well as a less costly alternative to conventional OLED manufacturing, which is currently based on rigid glass substrates.
OLEDs enable high-contrast, low-energy displays that are rapidly becoming the dominant technology for advanced electronic screens. They are already used in some mobile phones and small-scale applications, and increasingly in general lighting applications. Current state-of-the-art OLEDs are produced using glass doped with heavy metals to achieve high efficiency and brightness, which makes them expensive to manufacture, heavy, rigid and fragile. Using plastic can substantially reduce production costs while providing designers with a more durable and flexible material for their products. [via]
Highest efficiency ever for flexible OLEDs – [Link]
Boeing-Spectrolab has developed a solar cell that can convert almost 41 percent of the sunlight that strikes it into electricity, the latest step in trying to drop the cost of solar power.
Potentially, the solar cell could bring the cost of solar power down to around $3 a watt, after installation costs and other expenses are factored in, over the life of the panel. The new cost information comes from Boeing, whose Spectrolab unit supplies searchlights and solar simulators, and the Department of Energy, which sponsored the project. Current silicon solar cells provide electricity at about $8 a watt, before government rebates. The goal is to bring it to $1 a watt without rebates or incentives.
Solar cell breaks efficiency record – [Link]