Optimized Interleaved Synchronous Buck Converter Design for a Two-Stage 3.6 kW Auxiliary Power Module in Electric Vehicles

As the automotive market demands improved driving range in electric vehicles (EVs), highly efficient power electronics solutions are a focal point for researchers. Specifically, the low-voltage high-current nature of auxiliary power modules (APMs) with power ratings in the kilowatt range pose a challenge in hindering overall driving range of EVs. Three-port converters (TPCs) enable a highly efficient and power dense means of integrating the DC-DC portion of the on-board charger with the APM in a consolidated solution. To minimize the volume of the three-winding transformer, integrating the TPC, a two-stage APM is assumed in this article in which the second-stage consists of a synchronous buck converter (SBC) capable of 48 V to 9–16 V at 3.6 kW. With a maximum current of 250 A, phase interleaving of the SBC is necessary to improve overall power conversion efficiency. To ensure a sufficient balance of total volume and power loss, a design optimization framework for the SBC is presented in this article. Considerations of parameter variation, device and passive losses, and choice of non-coupled versus coupled inductors are the basis of the developed analytical models used in loss evaluation and inductor design. Results of the framework for 2060 unique designs are presented wherein trade-offs for three optimal designs are discussed yielding the final hardware demonstrator. Experimental results for power conversion efficiency are compared to the analytical model yielding a root mean square error of ~0.24% over the converter operating range.