Power Electronics

Data Points

High-Efficiency Converter Design Receives Patent

U.S. Patent 7,254,047, “Power Converters Having Output Capacitor Resonant with Autotransformer Leakage Inductance,” was issued on Aug. 7, 2007. This is the seventh U.S. patent of the year to be awarded to CPES-VT researchers. The patent was submitted by Yuancheng Ren, Julu Sun, Ming Xu and Fred C. Lee.

According to the patent, “Power converters having reduced body-diode conduction loss, reduced reverse-recovery loss and lower switching noise, among other benefits, have a resonant capacitor (CR) connected across an unfiltered output.”

As illustrated in the figure, the basic concept described in the patent is the use of a resonant capacitor that resonates with the leakage inductances LK1 and LK2 of the power converter's transformer. The resonant capacitor and leakage inductance are selected such that one-half of the resonance period is equal to the on time of each secondary switch (S1 and S2). The resonance enables zero-current switching in these secondary switches. It also enables zero-body-diode conduction during dead times and eliminates reverse-recovery losses in these devices.

The use of a resonant capacitor is applicable to many different circuit topologies, such as active-clamp forward, push-pull forward and center-tap secondary, as well as the full-bridge topology shown in the figure. Converters that use this design feature provide high energy-conversion efficiency and high-frequency operation.

For more information, contact CPES industry liaison Teresa Shaw at [email protected].

Vendor Will Develop Ultracaps for Mercedes Hybrids

Mercedes Car Group has awarded Maxwell Technologies a contract to design and produce ultracapacitors for an advanced hybrid-electric drive-train program. This drive train will incorporate a braking energy-recuperation system that increases vehicle fuel efficiency and reduces emissions.

David Schramm, Maxwell's president and CEO, said that the contract provides for funding from Mercedes to develop a new BOOSTCAP ultracapacitor cell specifically designed to meet the energy-storage and power-delivery requirements of one of Mercedes' torque assist and recuperative braking systems.

“Mercedes-Benz is a global automotive technology leader, so working more closely with its research and development organization will give us the opportunity to demonstrate Maxwell's capabilities as a supplier for future series production programs,” Schramm said.

Chinese Servo System Market to Reach $1 Billion by 2012

Servo motor and servo drive (servo system) revenues in the Chinese market increased by an estimated 26.8%, or $361.6 million, in 2006, according to a recent report published by IMS Research (Wellingborough, United Kingdom). The market research firm predicts that the Chinese servo system market will maintain steady growth to reach about $953.8 million in 2011.

Servo systems account for more than 80% revenue of the total motion-controls market in China, per IMS Research. As the main impetus of growth to the motion-controls market, IMS Research says that servo systems are expected to grow at a compound annual growth rate (CAGR) of more than 20% in terms of revenue in the next five years. In contrast, stepper systems, says the market research firm, are forecast to grow at a modest 10% CAGR in terms of revenue over the same period.

Although the servo systems market is enjoying excellent growth, the competitive environment is rapidly evolving. The existing market framework, in which Western, Japanese and local suppliers seldom compete directly and primarily focus on a dedicated market, is changing due to Taiwanese and Korean companies entering the market in recent years, according to IMS Research. The firms says that local Chinese suppliers are facing more pricing pressure due to the entry of relatively low-priced Taiwanese and Korean products.

“Although the competitive environment of the Chinese servo systems market has changed dramatically in recent years, Chinese suppliers still have potential to increase their market shares quickly in [the] next five years,” notes IMS Research market analyst Reggie Li. “Chinese suppliers are getting mature both in technology and sales channel development. Government aid through R&D funds also helps the Chinese companies to develop more advanced products, which will help these companies compete on something other than price.”

Visit www.imsresearch.com for more information.

Foundry Enables High-Voltage SoC Applications

X-FAB Silicon Foundries, which specializes in the production of analog/digital integrated circuits, has enhanced its XH035 0.35-µm analog/mixed-signal platform to offer full modularity of device types for digital, analog, high-voltage and embedded nonvolatile memory (NVM) capabilities. This combination addresses the majority of advanced analog/mixed-signal and high-voltage design needs, while providing a cost-effective way for companies to choose only those options that match their specific requirements.

The process also enables smaller designs, as well as reuse of existing analog IP across different design projects. Furthermore, X-FAB has enhanced its existing 0.35-µm XH035 high-voltage devices to yield lower on-resistance in power devices at lower mask count.

The fabrication process supports a wide variety of active and passive devices to address analog/mixed-signal design needs. Among these are low-leakage and low-threshold core module options, additional primitive devices such as double metal-in-metal (MIM) capacitors, 10-kΩ polysilicon resistors and Schottky diodes, as well as high-voltage depletion and high-voltage thin-gate oxide transistors.

Embedded NVM options for the process include EEPROM and Zener Zap technologies. The process also comes with verified analog IP libraries, which serve as a starting point for companies to develop their own analog libraries that can be reused to achieve the greatest cost efficiencies. The fabrication process is available now for high-volume manufacturing. X-FAB also provides automotive-qualified dual sourcing.

For more information on the XH035 0.35-µm analog/mixed-signal platform, visit www.xfab.com.

Electrolyte Chemistry Creates High-Temperature Supercapacitors

CAP-XX's HS and HW supercapacitors feature a higher boiling-point electrolyte that extends the maximum operating and storage temperature from 75°C up to 85°C (-40°C minimum). It also extends the maximum operating voltage from 4.5 V up to 5.5 V. Therefore, these supercapacitors work reliably in devices where nearby components can get very hot, such as RF power amplifiers, which can reach 120°C during transmission. They are also suitable for devices exposed to high-temperature environments (such as the engine compartment in an automotive application).

The supercapacitors also benefit from a unique nanotechnology construction in which charges are stored on nanoporous carbon electrodes deposited on aluminum foil, arranged in multiple layers and connected in parallel to minimize resistance and maximize capacitance. The technology provides the HW series with capacitance ratings to 0.4 F and an ESR below 100 mΩ at 5.5 V. The HS series is rated to 0.7 F and an ESR below 55 mΩ at 5.5 V. The supercapacitors also have power densities reaching 71.5 kW/L and energy densities up 1.5 Wh/L. The pulse current for a single pulse is 20 A, and rms currents up to 4 A are supported.

For additional information, visit www.cap-xx.com.

Product Teardowns Offer a Peek Inside

At the upcoming Power Electronics Technology exhibition in Dallas, component suppliers will give engineers a glimpse at the power components within various end products or components. One vendor, Analog Devices will showcase an electronic energy meter containing some of its ICs. Meanwhile, Freescale plans to present a teardown of a mobile phone product to show the power management components within. Another company, Fero Solutions will show attendees the inner workings of its Vibration Energy Harvester.

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