Power Electronics

Data Points

DOSA Defines New Standard for POLs

The Distributed-power Open Standards Alliance (DOSA) has announced a second-generation standard footprint and pin-out design for 3-A and 6-A nonisolated point-of-load converters (POLs). The new POL standard, which is based on Tyco Electronics Power Systems' PicoTLynx product, nearly doubles the current density (A/in2) from the alliance's first-generation standards to meet industry demand for high-density POL modules.

The standard establishes the location of pins, recommended pad layout on customer boards, input- and output-voltage ranges, and critical features and parameters required for interoperability and second sourcing.

Wake Forest University Doubles Plastic Solar Cell Efficiency

Researchers at Wake Forest University's Center for Nanotechnology and Molecular Materials (Winston-Salem, N.C.) say that they have pushed the efficiency of plastic solar cells to more than 6%. Previously, 3% had been the highest efficiency ever achieved for plastic solar cells, until 2005 when David Carroll, director of the Wake Forest nanotechnology center, and his research group announced they had come close to reaching 5% efficiency.

The group's goal now is to reach 10% in the next year, according to Carroll, who is also associate professor of physics at Wake Forest. “I fully expect to see higher numbers within the next two years, which may make plastic devices the photovoltaic of choice,” Carroll says. According to researchers, to be considered a viable technology for commercial use, solar cells must be able to convert about 8% of the energy in sunlight to electricity.

In a paper to be published in an upcoming issue of the Applied Physics Letters journal, Wake Forest researchers describe how they have achieved record 6% efficiency for organic or flexible plastic solar cells by creating “nano-filaments” within light-absorbing plastic, similar to the veins in tree leaves. This allows for the use of thicker-absorbing layers in the devices, which capture more of the sun's light, according to the researchers.

Because they are flexible and easy to work with, plastic solar cells could be used as a replacement for roof tiling or home-siding products, or incorporated into traditional building facades. These energy-harvesting devices could also be placed on automobiles. Because plastic solar cells are much lighter than the traditional silicon solar panels, which convert about 12% of the light that hits them into useful electric power, structures do not have to be reinforced to support additional weight.

A large part of Carroll's research is funded by the U.S. Air Force, which is interested in the potential uses of more efficient, lightweight solar cells for satellites and spacecraft.

Startup Begins Sampling SiC Transistors

TranSiC, a spin-off from the Royal Institute of Technology, KTH in Kista, Sweden, has begun sampling bipolar power transistors fabricated in silicon carbide to a few selected test sites. The company will be in a position to sample chips, packaged devices and multichip modules before the end of the 2007 summer, says Bo Hammarlund, TranSiC's CEO.

Founded in 2005, TranSiC was initially supported by VINNOVA, the Swedish Governmental Agency for Innovation Systems, and the Swedish Energy Agency. TranSiC designs, manufactures and sells its silicon carbide power transistor components, BitSiC, to the international industry. BitSiCs have very low switching losses, high breakdown voltages and can handle high currents. Example applications include compact motor controls at power levels greater than 1 kW, such as may be required in hybrid electric vehicles. For more information, see www.transic.com or e-mail [email protected].

High-Density Power Supply Features Mechanical Flexibility

A 350-W ac-dc converter from XP Power packs a power density of 11.2 W/in3 in a U-channel package that can be mounted either horizontally in a 1U space or vertically in a 2U space. The MFA350 power supply, which measures 3.2 in. × 6.8 in. × 1.5 in., generates a 12-V, 24-V or 48-V output while operating from a universal input-voltage range. The company will also offer a version for -48-V input.

The supply includes a 12-V, 1-A fan supply; a 5-V, 0.3-A standby supply; and a full-featured signal set including ac fail, dc OK, remote on/off, active current sharing and remote sense. The unit delivers full power from -10°C to 50°C, and operates up to 70°C with derating.

The MFA350 is 86% efficient, so only 13 cfm of airflow is needed for full output power. The company attributes its high power density and efficiency to several design techniques. For example, on the primary side of the power supply, a dual FET switch topology eliminates the need for a passive snubber, and in the PFC boost stage, a SiC diode is used in place of a silicon rectifier. Both techniques improve efficiency.

Another design trick is the use of triple-insulated wire in the main transformer, which enables it to achieve higher power dissipation. In addition, an onboard power-supply circuit sequences the order of turn on of the MFA350 and the customer's circuitry.

The power supply is priced at $175 each in OEM quantities. For more information, see www.xppower.com.

U.S. Primary and Secondary Battery Demand to Approach $15 Billion in 2011

U.S. demand for primary and secondary batteries is expected to increase 4.3% annually through 2011, reaching $14.9 billion, according to a new study by The Freedonia Group (Cleveland, Ohio). The market research firm has found that growth will be driven by such factors as strong demand for battery-powered products like mobile phones and digital cameras, and heightened production of light motor vehicles. According to the “Batteries” study, market gains will also be assisted by an ongoing shift in the product mix toward more expensive batteries that deliver improved performance for high-drain electronic devices.

Sales of primary batteries are expected to rise faster than secondary types through 2011, bolstered by increasing usage of primary lithium and other high-performance battery chemistries in high-drain applications such as digital cameras, as determined by the study. The recent introduction of the nickel oxyhydroxide primary battery chemistry, which can deliver more power and longer run times in many applications, will also support primary battery growth, according to The Freedonia Group.

The research firm also says that consumer applications will continue to account for 72% of all primary battery sales value in 2011, and that demand for replacement primary batteries will benefit from the burgeoning number of battery-powered portable devices in use such as digital cameras. Primary battery sales gains will be aided by rising durable goods production levels, according to The Freedonia Group.

Although alkaline batteries will remain the dominant primary battery type, accounting for 70% of sales in 2011, other types such as primary lithium and zinc-air will grow faster, as predicted in the study. Primary lithium batteries will post the fastest gains of all primary battery types, says the market research firm.

The study found that sales of secondary batteries will increase 4% annually through 2011 to $9.1 billion, lagging overall battery demand. Although falling manufacturing costs of such advanced rechargeable chemistries as Li-ion and nickel-metal hydride will restrict gains in value terms, demand will be supported by a shift in the product mix toward advanced electronic devices such as MP3 players and multifunction mobile phones, says The Freedonia Group.

The expanding hybrid motor vehicle market also will bolster demand for advanced rechargeable Li-ion and nickel-metal hydride batteries, finds the study. As a result, says the market research firm, these battery chemistries will see the fastest gains in the secondary battery market. According to the study, lead-acid batteries will continue to dominate the secondary battery market, accounting for nearly 70% of sales in 2011. For more information, see www.freedoniagroup.com.

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