Adjustable Frequency–Duty-Cycle Hybrid Control Strategy for Full-Bridge Series Resonant Converters in Electric Vehicle Chargers

In this paper, an effective output voltage control method using adjustable frequency-duty-cycle hybrid control is presented. By using the proposed method, the operating performance of the full-bridge series resonant dc-dc converter applied to the onboard charger in electric vehicles under the constant-voltage charge mode is improved. The proposed control method improves the system efficiency of the charger up to 4% for light load conditions compared with the conventional control method without any extra hardware. A theoretical analysis is described along with a loss analysis in detail, and the validity of the proposed method is verified by experiment with a 3.3-kW prototype onboard charger.