Design and Performance Analysis of a High-Efficiency Bidirectional DC-DC Converter for Electric Vehicle Battery Systems

Abstract

Electric vehicles (EVs) rely on efficient, compact, and reliable power conversion between the high-voltage battery pack and the DC traction bus that feeds the motor inverter and auxiliary loads. This paper presents the design, modeling, and simulated performance analysis of a high-efficiency bidirectional DC-DC converter intended for EV battery interfacing applica-tions, including motoring (battery discharge / boost mode) and regenerative braking or grid-charging (buck / charge mode). A non-isolated, two-phase interleaved synchronous buck-boost topology built around silicon-carbide (SiC) MOSFETs is pro-posed to minimize conduction and switching losses while keeping component count and cost low relative to isolated topologies such as the dual active bridge (DAB). Analytical design equations for the power inductor, DC-link capacitors, and semiconductor devices are derived for a 400 V DC bus and a 300–400 V lithium-ion battery pack rated at 5 kW continuous power. A dual-loop (voltage-outer, current-inner) proportional-integral (PI) control scheme with automatic buck/boost mode arbitration is described. A loss model comprising conduction loss, switching loss, and inductor core/copper loss is used to predict converter efficiency across the load range. Simulated results indicate a peak efficiency of approximately 97.4% near 60–70% of rated load, with efficiency remaining above 94% down to 10% load, an inductor current ripple below 20% of rated current, and a DC-bus voltage ripple under 1.5%. The interleaved structure is shown to halve the effective ripple frequency seen by the input and output capacitors, enabling a reduction in passive component size of approximately 35–40% compared with an equivalent single-phase design. The results support the suitability of the proposed converter for EV battery management systems requiring high efficiency, bidirectional power flow, and fast dynamic response during regenerative braking events.