Resonant converters: properties and applications for variable loads

This paper summarizes a complementary lesson on resonant converters intended for under-graduate students finalizing the industrial engineering program (equivalent to MSc Electrical Engineering) or post-graduates initiating the PhD program that begin their research activities on power electronics. The contents motivate the students to find suitable resonant converter applications of industrial interest. An approach to resonant converters is presented 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 (HID) lamps and power supplies for electrical discharge machining (EDM).