Coupled Magnetic-Based Integrated Isolated Onboard Battery Charger and Boost Motor Drive Unit for Electric Vehicles

This article discusses a power converter that integrates a boost motor drive and an onboard battery charger into one module unit for a drive system less than 30 kW. The proposed circuit uses a coupled magnetic-based device (CMD) in the boost converter (BC), which can switch between a boost inductor and an isolated transformer, with respect to the boost motor drive and ac charging operation. In order to achieve high power density and high efficiency, a newly four-leg CMD is proposed. Comparing to the three-leg CMD, the power density is increased by 12%, and the efficiency can be increased by 1.5%. As a result, the drive efficiency can be improved by 2.5% comparing to a standard nonboost motor drive. The details of the proposed circuit structure and the CMD configuration are discussed in this article. An A4-size prototype that used GaN-FETs was built to show the validity of the proposed circuit. Experimental results show well agreement with the calculated and simulation results, where a 5-kW boost motor drive with 48 V and a 3-kW AC100V charging were achieved in the built prototype. The motor drive efficiency is 96% at 3 kW with direct drive and 94.8% at 5 kW with boost drive, and the AC100V charging achieved 90% efficiency at 3 kW.