This paper proposes a maximum efficient point tracking (MEPT) algorithm for CLLC converters in on-board chargers (OBCs) of electric vehicles. In the resonant network of the LLC, the resonant capacitors and magnetic components suffer from parameter variations caused by manufacturing tolerances and thermal degradation, which lead to inevitable shifts in the resonant frequency. Furthermore, when PWM control is applied to support a wide output voltage range, the PWM duty ratio affects switching losses, which may result in efficiency degradation. The proposed MEPT algorithm supplies stable charging current to the battery while computing efficiency in real time and adjusting the PWM duty ratio to follow the optimal efficiency point. A 7.3 kW prototype validates the approach, achieving an average efficiency improvement of approximately 0.4% compared with conventional control.
.jpg "Jaehyeok Jang (he/him/his) photo")