Investigation of electrical safety for non-isolated single-phase on-board chargers used in BEV/PHEV

This paper proposes a non-isolated single-phase onboard charger (OBC) for use in EV/PHEVs to meet electrical safety which is mainly caused by common mode currents. The non-isolated OBC must not only pass the touch current test (human body impedance voltage drop less than 250 mVrms) but must also prevent the residual current (RCD) device trip (trip current is 30 mA) by large ground leakage current due to the low common mode impedance compared to the galvanic isolated OBC. Therefore, the authors use a T-type PFC and active power decoupling circuit. The effectiveness of human impedance voltage drop reduction and ground leakage current reduction is verified through suitable experiments. These values are confirmed as under the limit value defined by the relevant standard.