DC/DC Converters for High Conversion Ratio Applications - A comparative study of alternative non-isolated DC/DC converter topologies for high conversion ratio applications

Abstract

This thesis investigates how alternative topologies to the standard buck converter can be used in applications with a high voltage conversion ratio. The purpose is to match high demands on voltage conversion ratios and efficiency without a considerable increase in cost and footprint size. Five alternative topologies are identified, four of these are compared through simulations. Simulation models were built with component models from manufactures and the setup where focused on comparing characteristics dependent on topology design. Two topologies show an improved performance compared to the standard buck converter. One topology is the tapped inductor buck which is based on different effective inductance during the charge and discharge phases of the converter. The other topology, SEPIC fed buck, a parallel converter technology which creates multiple paths for the energy which reduces the I2 losses. The thesis concludes that it is possible to increase the efficiency with approximately 1% with an alternative topology and it also result in a longer duty cycle. The trade-off is a slightly increased size and increased cost due to the use of coupled inductors which needs to be custom made.