Absolute Minimum Deviation Controller for Multi-Level Flying Capacitor Direct Energy Transfer Converters

This paper introduces a dual-mode controller for multi-level flying capacitor (ML-FC) converters that provides theoretically minimum possible voltage deviation (absolute minimum), seamless mode transitions, and flying capacitor size reduction. These advantages are obtained by introducing a switching state that is not utilized during regular converter operation and the development of a simple capacitor peak/valley current matching technique. The effectiveness of the controller is verified with a 3.3 V, 15 W, 400 kHz frequency (800 kHz ripple frequency) three-level flying capacitor buck converter prototype.