In this paper, we present a physically based model of power diodes. The model is based on the numerical solution of the ambipolar diffusion equation using a modified finite difference method. The model is implemented using Matlab. Optimization routines are executed within Matlab to extract the design parameters of the power diode under investigation. Comparisons between the results of the Matlab model with Silvaco mixed-mode simulations are presented. The model is used to extract design parameters of selected power diodes whose experimental waveforms are given.