The use of FPGAs (Field Programmable Gate Arrays) in HIL (Hardware-in-the-loop) approaches is popular nowadays due to its high feasibility and fast speed. One of the common areas of application is power electronics. The implementations of power system models into FPGAs require the utilization of numerical methods to describe their behavior. This study presents the implementation of a buck converter model as an example of a power supply using the Improved Polygon numerical method. It is shown that this method significantly improves the resource utilization and minimum computation step in comparison with the well-known 2 nd order Runge-Kutta method, while the accuracy results of both methods are nearly the same. Therefore, the use of Improved Polygon method is proposed for power electronics systems instead of the 2 nd order Runge-Kutta method. Implementation details, accuracy evaluation and synthesis results are presented and analyzed. The results show a decrease up to 48% in area usage and 23% decrease in computation step.