Monday, November 06, 2006

Electricity from Sugar Water

A new way to make hydrogen directly from biomass, such as soy oil, reported in the current issue of Science, could cut the cost of electricity production using various cheap fuels.


Researchers at the University of Minnesota have developed a catalytic method for producing hydrogen from fuels such soy oil and even a mixture of glucose and water. The hydrogen could be used in solid-oxide fuel cells, which now run on hydrogen obtained from fossil-fuel sources such as natural gas, to generate electricity. Further, by adjusting the amount of oxygen injected along with the soy oil or sugar water, the method can be adapted to make synthesis gas, a combination of carbon monoxide and hydrogen that can be burned as fuel or converted into synthetic gasoline. The method can also produce chemical feedstocks, such as olefins, which can be made into plastics.


Although the results are preliminary, the new catalysis process represents a fundamentally new way to directly use soy oil and other cheap biomass as fuels; such biomass now needs to be converted into biodiesel or ethanol in order to be used as fuels. "Generally, people have steered clear of nonvolatile liquids--materials that you cannot vaporize," since these typically produce a carbon residue that stops the process of producing hydrogen, says Ted Krause, head of the basic and applied research department at Argonne National Laboratory, in Argonne, IL. By eliminating the need to process soy oil and sugar water to make volatile fuels such as ethanol, the new method "opens up the number of available biomaterial feedstocks," he says.


The process begins when the researchers spray fine droplets of soy oil or sugar water onto a super-hot catalyst made of small amounts of cerium and rhodium. The rapid heating combined with catalyst-assisted reactions prevents the formation of carbon sludge that would otherwise deactivate the catalyst. And the reactions produce heat, keeping the catalyst hot enough to continue the reaction. As a result, although fossil fuels are used initially to bring the catalysts up to the 800 °C working temperature, no fossil fuels are needed to continue the process. "One of the virtues of our process is it requires no external process heat--it drives itself," says chemical-engineering and materials-science professor Lanny Schmidt, who led the research.

Source:www.technologyreview.com
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Super-vivid, super-efficient displays

Your next MP3 player may sport more-vivid color displays and longer-lasting batteries. That's because a major manufacturing effort by South Korea's Samsung SDI could help bring a display technology called organic light-emitting diodes, or OLEDs, into the mainstream. Until now, OLED displays have not been manufactured in high volumes, and applications have generally been limited to Asian markets.


OLEDs are based on a light-emitting conductive organic molecules that consumes one-half to one-fifth of the power of liquid-crystal displays (LCDs). Displays using OLEDs present more-vivid colors and allow for clearer videos, thanks to a faster "refresh rate." As the technology matures and cheapens, it could ultimately replace current computer-monitor and television technologies.


While other electronics companies are in the planning stages for ramping up manufacture and adoption of OLEDs, Samsung is spending $500 million to build an OLED factory that will begin production next year. Samsung hopes to churn out between one million and two million displays per month, initially for cell phones and other mobile devices that would move beyond Asian markets, says Barry Young, an industry analyst.


The Samsung effort (see Samsung's technology explainer here) includes technology from Universal Display, of Princeton, NJ, which pioneered an OLED variant that uses phosphorescent molecules to produce the reds, blues, and greens necessary for a color display with very high efficiency.


Stephen Forrest, vice president of research at the University of Michigan, whose research group (originally at Princeton University) licensed its OLED technology exclusively to Universal Display, believes the Samsung factory is a huge milestone. "We are at a very critical frontier," he says. "This is a good technology, and people know it, so now it's a matter of getting more companies committed to entering into manufacturing. To make a better, cheaper, more efficient display is a very important part of our everyday life."

Source:www.technologyreview.com
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LED Driver Supports Multi-Mode Operation

Catalyst Semiconductor’s high-power, 500-mA inductive boost LED driver is designed for Movie/Flash mode applications. The CAT4134 offers a fully integrated Movie/Flash switching function, which allows designers to set the exact Flash and Movie modes required via a single resistor, minimizing the need for external circuitry. Capable of driving up to six white/color LEDs, the CAT4134 is ideal for increasing efficiency and simplifying the design of video lighting applications.


The new Catalyst inductive boost LED driver offers dual channel outputs, which provide matched LED currents of up to 250 mA per channel. Output current levels are controlled by one of two resistors, RSET or RFLASH. When the flash input pin is low (Movie mode), RSET controls the LED current. When the flash input pin is high (Flash mode), the resistor RFLASH controls the LED current. Each channel drives two or three white LEDs in series and provides a regulated current to control LED brightness. Input supply down to 3 V is supported, making the device ideal for Li-Ion battery applications.


High frequency, low noise operation allows the CAT4134 to be used with small external inductors and ceramic capacitors while retaining up to 85% efficiency. When disabled the device can be placed into a “Zero” quiescent mode via a shutdown pin, eliminating battery drain when not in use.


The CAT4134 is available in a 3-mm x 3-mm, 12-pin TDFN RoHS-compliant package. Pricing for 10,000-piece quantities is $0.88 each. Samples and evaluation kits are now available.

Source:www.powerelectronics.com
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Friday, November 03, 2006

Thermal Solutions Provider Licenses Heat Transfer Technologies

Celsia Technologies has entered a multi-year agreement with Taiwan-based Yeh-Chiang Technology (YCTC), a manufacturer of heat pipes. Under the terms of the agreement, YCTC will manufacture Celsia’s thermal management products in China. YCTC will also license Celsia’s patented thermofluidic technology to offer to its key OEM customers.


“Celsia’s technology is exactly what the market needs today,” said John Yang, founder of YCTC. “With Celsia’s new vapor chamber technology and its thin, flat form factors, customers can have greater flexibility and simplicity in their electronic designs and assemblies. We believe this technology is the next step for electronics heat transfer, and it will provide great differentiation to our customers.”


“We are building partnerships across the electronics supply chain so that in addition to our strong technical position, Celsia is equally strong in its distribution and supply network,” said George Meyer, Celsia’s chief marketing officer and general manager of the Americas and Europe. “YCTC is an excellent heat pipe manufacturer with a laser focus on manufacturing two phase heat transfer products. The combination of Celsia technology and YCTC manufacturing will be a formidable force in the market.

Source:powerelectronics.com
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Thursday, November 02, 2006

Rerouting Brain Circuits with Implanted Chips

New, implantable and wireless brain chip can create artificial connections between different parts of the brain, paving the way for devices that could reconnect damaged neural circuits. Scientists say the chip sheds light on the brain's innate ability to rewire itself, and it could help explain our capacity to learn and remember new information.


"We have a chance of manipulating and repairing [specific] regions of the brain that might be damaged," says Joseph Pancrazio, director of the neural-engineering program at the National Institute of Neurological Disorders and Stroke in Bethesda, MD. "To be able to repair these kinds of lesions on a neuron-by-neuron basis is extraordinary."


In stroke and spinal-cord injuries, neural circuits may be damaged, leaving patients with profound problems in movement or speech. In recent years, scientists have begun developing brain-cognitive interfaces, which record neural signals and transmit them either to a computer, to another part of the brain, or to another body part in effort to get around the neural blockade.


In the new study, researchers from the University of Washington, in Seattle, showed for the first time in live animals that an implantable device could record signals from one part of the brain and transmit that information to another part, reshaping neural connections in the process. "We essentially set up an artificial-feedback loop between two different parts of the cortex," says Eberhard Fetz, the scientist who led the study.


The device, built entirely of off-the-shelf parts, consists of tiny wire electrodes surgically implanted into a monkey's motor cortex. (Neurons in this area are active when an animal makes a voluntary movement.) The wires record activity from these cells and send the signals to a tiny printed circuit board, which amplifies and processes the signal. That information is then sent to a neighboring circuit board and electrode, which uses the signal to stimulate cells in another part of the motor cortex. The entire apparatus is encased in titanium and attached to the monkey's head, allowing the animal to go about its normal daily activities.


According to research published online in Nature, the device was able to reshape the neural circuits that control muscle movement. At the start of the experiment, neurons at the recording sites triggered movement of the wrist in a different direction than when neurons at the stimulating site were activated. After running the record-stimulate sequence for 24 hours in freely behaving monkeys, researchers found that underlying neural circuits had changed: the wrist movement associated with neurons at the stimulating site more closely resembled the movement associated with neurons at the recording area, indicating that the neural connections between these two areas had strengthened.

The findings support a long-held theory in neuroscience: that activating different brain cells at the same time strengthens connections between those cells. Scientists believe this concept underlies our ability to both learn new information and recover some motor and cognitive function after strokes and other brain injuries. "The findings show that the current conception of long-term strengthening is very much on the right track," says Krishna Shenoy, a neuroscientist at Stanford who is also developing neural implants

Source:www.technologyreview.com
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TPS40140 Synchronous PWM Controller

Although new technologies based on digital power control promise to be disruptive technologies in the long run, mainstream analog control technology can still have a significant and immediate impact on power system designs. Such can be said for this year's Power Electronics Technology Product of the Year award winner. The TPS40140 synchronous PWM controller from Texas Instruments (TI) is, at heart, an analog controller. However, because of its clever design techniques, the chip simplifies the potentially complex task of paralleling voltage sources to create scalable point-of-load (POL) power designs.

The TPS40140 features a unique characteristic that the vendor calls “stackability.” That term describes the way multiple controller ICs can be combined in a single design either to scale current levels on a given output or to add additional voltages. A single TPS40140 can be configured to generate two independent outputs or configured as a 2-phase controller with a single output. Then, by stacking or paralleling controller chips, designers can increase current output on a given voltage rail. The controller supports up to 16 phases of interleaved operation for up to 320 A of output.

The resulting design can be a mix of single- and multi-phase outputs (see the figure). Interleaved operation not only permits the scaling of current levels, but also reduces ripple current and requirements for input and output capacitance.

Although existing multiphase controllers can be cascaded to scale the number of phases, they typically employ an analog interface to control phasing of the different outputs. In contrast, the TPS40140 employs a unique digital interface to control phasing, which makes the designs less sensitive to noise and eases pc-board layout.

In a multicontroller, multiphase design, one channel generates a master clock (CLKIO). This clock is distributed to the slave channels, which use it to generate their PWM clocks. The master clock runs at eight times the frequency of the slave PWM clock. In other words, within each master clock signal there are eight frames (seven clock pulses plus a missing pulse for synchronization), and each PWM slave clock will trigger on a different frame depending on the phase number assigned to that PWM channel. That phase number is programmed using a simple voltage divider connected to the phase select pin on each channel.

In designing this part, TI overcame several design challenges. According to Stefan W. Wiktor, dc-dc controller design manager at TI, one of the most difficult was achieving good current balance among phases when the phases are generated across multiple controller chips. This is because of the difficulty in matching PWM ramp signals from chip to chip. TI addressed this problem using a frequency-to-current converter that makes the PWM ramp signal independent of semiconductor process-related parameters, except for reference voltage, which is very controllable.

Though just introduced in August 2006, the TPS40140 has already experienced design wins at two major power-supply companies, a large server manufacturer and a test equipment manufacturer. However, Tim Goodrow, product marketing manager for dc-dc modules at TI, observes that customers are adopting the TPS40140 because of the ease with which this controller implements multiphase control, more so than for its flexibility in generating multiple voltages.

Source:www.powerelectronics.com
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Wednesday, November 01, 2006

Rectifier IC boosts

Increasing system efficiency by 1% over discrete solutions, the IR1166 SmartRectifier IC simplifies the design of mid-power secondary synchronous rectification (SR) circuits of resonant half-bridge converters and flyback converters designed for 50 to 150-W discontinuous conduction mode, critical conduction mode, and continuous conduction mode. The part uses a technique for precise, direct sensing of voltage thresholds across the SR MOSFETs.

Specifications include a VCC of 20 V, a VFET of 200 V, a maximum switching frequency of 500 kHz, a gate drive of 1/–3.5 A, a VGATE clamp voltage of 10.7 V, and a maximum sleep current of 200 µA. The part is housed in an SO-8 package and will soon be in a DIP-8 package. The IRAC116-100W flyback reference design is also available. ($0.70 ea/10,000—available now.)

Source:www.electronicproducts.com
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