Dc-dc Power Conversion at Very High Frequencies

Modern applications are driving demand for power systems with capabilities beyond what is presently achievable. High performance systems, like radars and medical imaging systems impose challenging specifications on power density and bandwidth that are difficult to achieve with current circuit topologies. Power density can be improved with better semiconductor components and passive elements, and by reducing the energy storage requirements of the system. By dramatically increasing the switching frequency, it is possible to reduce the energy storage requirements and improve bandwidth. In this seminar, we will discuss the development of system architectures and circuit topologies for dc-dc power conversion at very high frequencies (> 30MHz). The systems architectures that are developed are structured to overcome limitations associated with conventional designs. In particular, the new architectures described here structure the energy processing and control functions of the system in such a manner that high efficiency can be achieved across wide load range while regulating the output. We will discuss circuit designs that are well suited to these new architectures as well as provide details on gate drive strategies for MHz switching One of the gating schemes discussed, provides near theoretical minimum loss by resonantly wave shaping the gate voltage to have a trapezoidal drive voltage. This waveshaping approach is then taken a step further, yielding a new class of dc-dc converter that archives a significant reduction in peak switch voltage stress, requires small passive components with low energy storage, and provides the capability for extremely rapid startup and shutdown. This new class of converter is well adapted to the architectures and gate drive methods described here. It is expected that the new architectures and circuit designs discussed here will contribute to the development of power converter having greatly reduced size and improved transient performance.
Professor Rivas recently joined the faculty of EECS at the University of Michigan. Prior coming to Michigan he worked for the General Electric Global Research Center developing power electronics for medical imaging and aviation systems. He received the B.A.Sc. degree in Electrical engineering from the Monterrey Institute of Technology in 1998. He obtained his Masters (2003) and doctoral degree (2006) at the Massachusetts Institute of Technology. His research interests are in power electronics, RF power amplifiers, resonant converters, soft switching topologies and control of power converters.