DESIGN AND VALIDATION OF A 1300 W HIGH-FREQUENCY PFC–LLC BATTERY CHARGER FOR 48 V LIFEPO₄ ELECTRIC VEHICLE PACKS

Abstract

Electric vehicles require the development of efficient and reliable on-board and off-board chargers. These chargers should be able to ensure the safe operation of the vehicle’s battery. In this paper, the design and validation of a 1.3 kW high-frequency switched-mode power supply (SMPS)-based electric vehicle battery charger with a wide input voltage range of 190 V to 265 V AC and a closed-loop control for the regulation of the DC-link voltage and the control of the battery charging process are presented. The proposed charger configuration includes a continuous conduction mode (CCM) active power factor correction (PFC) boost converter for current regulation, a high-frequency LLC resonant DC–DC converter for galvanic isolation, and zero-voltage switching (ZVS) of the converter. The proposed charger is designed to operate at a 51.2 V nominal battery voltage, a maximum battery charging voltage of 58.4 V, and a maximum charging current of 20 A. The control strategy of the proposed charger comprises a multi-loop control strategy with a DC link voltage control loop and a current control loop for the PFC converter, a constant current/constant voltage control strategy for the battery charger circuit, and a frequency modulation control strategy for the LLC converter circuit. The analytical results show that the input power factor is always greater than 0.98, and the efficiency is always greater than 93%. It is also shown that the output voltage ripple is within 1%, and the output current ripple is within 2.5%. Various protection schemes are provided for input over current protection, output over voltage protection, under voltage protection, overload protection, and earth leakage protection. The proposed high-frequency PFC–LLC structure provides a compact solution with low switching losses and high efficiency, which is not possible with conventional low-frequency chargers.