Teaching Resonant Converters: Properties and Applications for Variable Loads

This paper summarizes a lesson on resonant converters included in the new course, Advanced Power Conversion Techniques, within the M.Sc. program in electrical engineering at the University of Cantabria, Spain. The course has recently received the National Accreditation for official programs. The M.Sc. program, along with the Ph.D. thesis, forms a Ph.D. program in industrial engineering. The contents motivate the students to find suitable resonant converter applications of industrial interest. A new approach to teaching resonant converters is presented that focused on their properties at certain frequencies, such as for voltage sources, current sources, or sink and power source operation with very variable loads. The analysis of the converters enables the identification of these operating points and, by means of a sensitivity analysis with respect to the components of the resonant tank, explains the robustness of their behavior. Using as a starting point the fulfillment of the desired property, we propose that the students develop open-loop designs, with stable behavior, or closed-loop designs, with very small variation in the operating point. Two practical application examples are shown: electronic ballasts for high-intensity discharge lamps and power supplies for electrical discharge machining.