A Design Methodology for a Partial Power PSFB DC-DC Converter for Battery Charging

This paper presents a detailed design methodology for a Phase-Shifted Full Bridge (PSFB) topology-based Partial Power Processing (PPP) converter for battery charging applications. Unlike conventional DC-DC converters, the battery voltage variation imposes significant design challenges on the partial power converter. The wide battery voltage variation results in a wide duty cycle variation (as low as 10% to as high as 95%) over the entire operating range. The PSFB converter design becomes challenging, so an improved design methodology is proposed that looks at the converter operation holistically over the entire operating range. Variations in different parameters, like ripple in the filter inductor current, switching frequency, and duty cycle are accounted for in the proposed design methodology, along with a focus on Zero Voltage Switching (ZVS) over the entire duty cycle range. A working prototype of 1.5 kW is developed, and hardware-based experimental results are obtained. The softswitching boundaries predicted by the model are experimentally verified, and efficiency results are presented to highlight the benefits of the proposed design methodology. With a downscaled partial power converter, rated to handle only 35% of the battery power, peak system efficiency of $\mathbf{9 7. 5 \%}$ is reported experimentally. The impact of the snubber circuit on the overall system efficiency is presented as well.