Power Electronics

University Researchers Receive Power Electronics Patents

Last year, Virginia Tech’s Center for Power Electronic Systems (CPES) received five patents on power electronics technologies. These patents cover various innovations in the design of dc-dc converters and solid-state switches.

Fred C. Lee, director of CPES; Jih-Sheng Lai, electrical and computer engineering faculty member; and Lizhi Zhu, a former visiting scientist now with Ballard Power Systems, invented the Accelerated Commutation for Passive Clamp Isolated Boost Converters (6,876,556). This invention offers an efficient and cost-effective bidirectional dc-dc converter that reduces switch voltage stress.

For example, this design allows smooth conversion between two sources of direct current (dc) such as between fuel cells and high voltage batteries. This capability provides appropriate current levels for driving an electric vehicle and for powering electrical components on the vehicle regardless of voltage. The technology has been adopted by Ballard Power Systems, a fuel cell company.

A second patent went to Lee, research assistant professor Ming Xu, and Ph.D. graduate Jinghai Zhou for a Multi-phase Interleaving Isolated DC-DC Converter (6,944,033). This converter was designed to provide more power, higher operating frequency, and much reduced switching losses to power the next generation of microprocessors, as well as other portable telecommunication and portable equipment.

Lee, Xu, and Zhou also received a patent for a Bridge-Buck Converter with Self-Driven Synchronous Rectifiers (6,859,372). This invention provides a more power-efficient and low-cost solution for controlling the high-frequency voltage/current rectifier (synchronous rectifier) commonly used in low-voltage, high-current dc-dc converters. This technology has been licensed by the Intellectual Property Protection Fund (IPPF), created by members of the CPES industry consortium, and applied to powering the microprocessor. According to Virginia Tech, this technology has been demonstrated to be the most efficient voltage regulator solution.

Other inventions from CPES that received patents are Emitter Turn-Off Thyristors (ETO) (6,933,541), invented by Alex Huang, formerly with CPES, and a Solid State DC Circuit Breaker (6,952,335), invented by Huang and electrical engineering Ph.D. graduates Xigen Zhou and Zhenxue Xu. The ETO is a solid-state switch for use in high-frequency power converters that can provide fast and dynamic voltage support, fast switching speed, rugged turn-off capacity, and voltage control and protection.

This invention earned a 2003 R&D 100 Award from R&D Magazine as one of the "100 most technologically significant products introduced into the marketplace over the past year." The circuit breaker is a high-speed, solid-state circuit breaker capable of interrupting high dc currents without generating an arc. It uses the ETO thyristor as the switch. For more information about patents at Virginia Tech, visit Virginia Tech Intellectual Properties at www.vtip.org.

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