A Class of Single-Sensor Balancing Techniques for Flying-Capacitor Odd-Level Converters

Flying-capacitor odd-level (FCOL) converters are prone to unbalanced operation in the presence of non-idealities such as timing mismatches, requiring active closed-loop balancing of the flying-capacitor (FC) voltages. In this work, a class of low-complexity balancing techniques for FCOL converters presented, in which balancing is achieved by only sensing the innermost FC voltage regardless of the number of levels. Balancing is achieved using phase shift modulation via a single balancing loop based on a standard proportional-integral (PI) controller, making the approach especially attractive for low-cost applications based on custom-designed analog or digital ICs. A novel design approach, based on deliberate mismatching of the flying capacitors, is also introduced and shown to improve the closed-loop dynamics of the balancing loop and of the unregulated FC voltages. Simulation and experimental results are carried out on 5, 7, and 9-Level converter case studies to validate the approach.