A high power density drivetrain-integrated electric vehicle charger

This paper presents a new architecture for an isolated level 2 on-board electric vehicle (EV) battery charger which is integrated with the EV's drivetrain dc-dc boost converter. The proposed charger leverages many of the existing stages of a highly efficient and power-dense composite-architecture-based drivetrain boost converter. This composite boost converter comprises a buck, a boost and a dc transformer (DCX) stage. In selecting the proposed charging architecture, four alternative approaches to drivetrain integration are identified, explored and compared quantitatively in terms of added weight and charging losses. Out of the considered approaches, the proposed charging architecture provides an effective tradeoff between additional weight and charging losses. This drivetrain-integrated charger adds only a bridgeless-boost-based power factor correction (PFC) ac-dc stage, plus an H-bridge and a single winding to the composite boost converter, to achieve high-power on-board charging functionality without substantial additional weight. A 6.6 kW prototype of the proposed charger has been designed and its PFC stage built and tested. The PFC stage uses a digital implementation of a current sensor-less control strategy and employs effective ways of mitigating zero crossing distortion. The proposed charger architecture reduces the additional weight required for the onboard charging functionality, while achieving greater than 97% peak efficiency for the added charger module PFC stage.