The FPGA (Field Programmable Gate Array) implementation of real-time Hardware-In-the-Loop techniques is constantly growing due to its high speed. However, hardware implementation of SMPS (Switched-Mode Power Supplies) introduces some challenges, because their equations are changed depending on the state of the switches. This becomes more important in multistep numerical methods, which use several previous values. This letter presents the implementation scheme of Adams-Bashforth method which allows the designer to correctly apply it to switching power converters. The global accuracy and utilization results of the approach are analyzed in the letter. The results show that the proposed modification makes sense due to the high accuracy improvement at the expense of a reasonable increase in resources.