Final Year Project

Project Title

Comparative Analysis of Silicon and GaN-based DC-DC Buck Converters using FPGA-Based Prototyping and Hardware-in-loop Testing

Description

The adaptability of Electric Vehicles (EVs) is severely hindered by their limited drive range. Although battery technology has notably improved, it is miles from matching gasoline in terms of energy density. Although larger batteries could increase the driving range, it would drastically increase the cost of EVs. In place of this, designing an efficient powertrain becomes paramount. Achieving high efficiency and power density in power converters can be achieved through the use of wide-bandgap (WBG) devices. WBG devices, such as Gallium Nitride (GaN) FETs, operate at higher switching frequencies compared to Silicon MOSFETs. This substitution results in an extended drive range of about 15% along with a lighter and more compact powertrain. In this research, we have designed a GaN-based EV powertrain for the Auxiliary Power Module (APM), which serves auxiliary loads such as power steering, air conditioning, and power windows, among others, to ensure a comfortable and seamless travel experience. The APM comprises DC-DC converters in a two-stage configuration. The first stage in this powertrain is a high-power isolated converter, which converts the voltage from 300V at the battery to 48V, from which power is tapped for some applications. The second stage is the non-isolated low-power DC-DC converter string, which converts the voltage from 48V to 12V, catering to the rest of the auxiliary loads. Our findings show that GaN-based converters for APM exhibit a high efficiency of 97% and high-power density in terms of very small passive elements such as inductors or capacitors. For controlled and consistent output voltage, a closed-loop controller has been designed, implemented, and tested on the FPGA Zedboard, showing exceptional results with a very high gain margin and phase margin of the controller.