In this paper, an improved electrothermal model of power diode has been developed. This improved model is based on the numerical solution of the ambipolar diffusion equation (ADE) for all levels of injection instead of high level injection only as usually encountered. The main local physical effects are taken into consideration. The proposed model is capable in tracing the electrical and thermal effects including self-heating of the device under practical operation (with current density levels ranging from few mA/cm(2) to few thousands of A/cm(2)). The model has been validated against measurements and other models showing close agreement for different circuits (DC forward characteristics, turn-on and turn-off) and different temperatures (over the range of 25-125 degrees C). The comparison shows that the presented model is superior in predicting the main circuit parameters needed for power electronic design. The transient thermal responses are demonstrated for both repetitive and single pulse modes. The presented results show that our model is suitable for full electrothermal simulations of power electronic circuits. (C) 2015 Elsevier Ltd. All rights reserved.