I'm trying to simulate the efficiency of an IGBT driven power module. With P_{in}=P_{out}+P_{loss}, the efficiency could be calculated as:

- eta=Pout/Pin
- eta=1-Ploss/Pin

As you can see in the model attached, I tried both ways with different models. At first using an ideal switch, then an IGBT with linear loss model (V_{f} and R_{on}), then with a thermal description, and finally with both combined. The maximum difference between calculated accuracies is about 1%, which is quite a bit.

So my question is: Which of the described ways is most accurate one?

Thanks in advance

Fabian