A Hybrid Digital Control System for Totem-Pole Isolated AC/DC Converters Used in Electric Vehicles

This article proposes a new digital control system for totem-pole isolated ac/dc converters operating in discontinuous conduction mode (DCCM). A hybrid combination of the new digital control system and existing control methods is implemented on an experiment prototype. The proposed hybrid control offers a flat efficiency curve over a wide range of operations. Moreover, a new synchronization timing method and a new variable frequency modulation (FM) are incorporated inside the proposed method to mitigate the current surge in the transformer current at turnover instants between positive and negative half-line cycles (HCSs). The proposed hybrid modulation uses a narrower range of switching frequency as compared to conventional methods. The proposed digital control system uses a unique semisquare-waveform pattern with a frequency synchronous with the line frequency (50 or 60 Hz). Due to this, each of the two output diodes in the center-tapped full-wave rectifier operates only in one-half of the line cycle. Zero current turn-on for the output diodes and reduced reverse-recovery losses are achieved. Experiment results demonstrate the superior performance of the proposed hybrid control method.