Solutions for Current Balancing in Multi–phase LLC Resonant Converters for Electric Vehicles Considering Scalability, Interleaving, and Phase Shedding Capabilities

Multi–phase LLC resonant converters provide high power density, increased efficiency, good thermal distribution, and enables interleaving to drastically reduce the output current ripple. In addition, phase shedding capability at reduced output current levels allows for high efficiency over a wide operating range. However, these topologies are susceptible to component tolerances that create significant current imbalances between the phases. This paper presents a thorough evaluation of the star– connected transformer with floating star point, switched controlled capacitor and common capacitor LLC converter topologies and control techniques to mitigate the load–sharing issues instigated by the component mismatches while examining their scalability, interleaving, and phase shedding capability. The phase–shedding capability of each topology is evaluated using the first harmonic approximation (FHA) model to derive the gain characteristics of the configurations at any number of active phases. In addition, the current–sharing performance of each configuration is analyzed by modeling the multi–phase LLC resonant converter topologies with their respective phase– balancing control methodologies.