To achieve high power density, onboard charger (OBC) and the auxiliary power module (APM) are electrically integrated in electric vehicles (EVs). A key challenge of the integration is the light-load and cross-load operation in simultaneous power transfer modes. Specifically in [1], at light loads, the OBC operates at very high switching frequency and dc bus-side switches tend to lose zero-voltage switching (ZVS). In this paper, a control for light-load and cross-load operation in the charging mode for integrated OBC and APM topology, proposed in [1], is presented. A smooth transition from variable frequency (VF) to fixed frequency (FF) control and vice versa is achieved with power hysteresis control. Finally, the experimental waveforms at light-loads, cross-loads and during transition from VF to FF control and vice versa in charging mode of operation are provided.
