A Novel Hybrid Mode Control for a Phase-Shift Full-Bridge Converter Featuring High Efficiency Over a Full-Load Range

A novel hybrid mode control technique for a phase-shift full-bridge (PSFB) converter is proposed in this paper. The proposed method can improve power efficiency under both the light-load and heavy-load conditions. The basic concept of the proposed control technique is to decrease the turns ratio to reduce the circulating current, hence resulting in lower circulating losses. However, the output voltage under heavy load may not be stabilized using phase-shift control if smaller turns ratio is utilized. Therefore, the proposed technique employs asymmetrical pulsewidth modulation to achieve higher output voltage. To further improve the efficiency, an adaptive dead-time control method, which determines the dead-time value according to the load level, is also proposed. To validate the correctness and effectiveness of the proposed method, a 480-W PSFB converter is constructed and experiments are carried out accordingly. Comparing with a conventional PSFB converter, the efficiency of the proposed method can be improved up to 3.2%, 1.3%, and 0.6% under light-load, 30% load, and full-load conditions, respectively.