Due to the high dependency between reliability of power device and its junction temperature, monitoring their thermal behavior in real time is very essential. In this paper, a lookup table-based electro-thermal real-time simulation model is developed to quickly estimate the junction temperature of the power devices. Output series interleaved boost converter with high voltage gain and low input current ripple, which is dedicated for fuel cell application, is selected as a case study. The thorough design and implementation process are presented and the developed model is simulated with a 200 nanoseconds time step on NI FlexRIO PXIe-7975R real-time platform. Moreover, the effectiveness and accuracy of the FPGA-based electro-thermal model are validated by comparison the results from PLECS software.