98.7% Efficiency 1200–48 V LLC Converter Using Triple Step-Down Converter With One-Inductor Technique Compliant With EVSE Level 1

The proposed LLC flyback converter converts the 1200 V of the electric vehicle supply equipment (EVSE) into a 48 V battery system. The triple step-down converter with one inductor (TSDC-OL) technique converts 1200–400 V, and the transformer steps it down to 48 V. The zero-voltage switching (ZVS) mechanism is used for each switching operation and the equivalent on-resistance $R_{\text {ON}}$ is reduced to 1/4.5 times that of the existing technology. The proposed reference voltage compensator (RVC) can accurately maintain the charging current at 25 A. Since the left half-plane zero error amplifier (LZEA) contributes to the LHP zero, it ensures the stability of the RVC and prevents periodic variations. When the battery charges to 48 V, the operation switches to constant voltage (CV) mode via burst operation control (BOC) comparison with a leakage-based ultralow $I_{Q}$ comparator (LUC) with 2 nA $I_{Q}$ leakage. Finally, the proposed LLC flyback converter meets EVSE level 1 requirements in constant current (CC) mode and achieves 98.7% efficiency.