I am doing a simulation, and having trouble on how best to accurately capture switching losses of the antiparallel diode of an ‘IGBT with diode’ component.
On page 4 of the PLECS tutorial, it is stated to include negative current and voltage with zero switching energy for accurate interpolation. The (body) diode conduction characteristic in the PLECS tutorial is imported into the thermal model as negative currents and voltages on page 5.
However, on page 7 of the datasheet I am using, switching loss characteristic of the diode is also given. The tutorial does not cover this, and I think it is because of the application. I would expect to use the switching loss for negative currents to capture the loss of the antiparallel diode (based on page 5 of the tutorial), but that seems to be at odds with what the tutorial says on page 4 about switching loss interpolation. I want to be sure if I am misapplying the content of the tutorial. What is the recommended way to go about this problem?
I have included the tutorial and datasheet in question.
As you suggested, in the buck converter application from the tutorial the MOSFET’s anti-parallel diode will never conduct and is always blocking. In this case describing the diode turn-on losses isn’'t a necessary part of the tutorial, and might lead to additional confusion.
PLECS supports third quadrant turn-on and conduction losses for switch with diode components. See the excerpt from the Thermal Modeling + Semiconductor Loss Specification + Losses of Semiconductor Switch with Diode section of the PLECS Manual.
Semiconductor switches with an integrated diode such as the IGBT with Diode model allow losses for both the semiconductor switch and diode to be individually specified using a single set of lookup tables. The conduction and switching loss tables for the semiconductor switch are specified for the same voltage/current regions as for the single semiconductor switch without diode. Due to the polarity reversal of the diode, the diode losses are appended to the loss tables of the semiconductor switch by extending the tables in the negative voltage/negative current direction for the diode conduction losses, and in the positive voltage/negative current direction for the diode switching losses. An example turn-off loss table and conduction loss profile for a semiconductor switch with diode are shown in the next two figures. A summary of the valid voltage and current regions for defining conduction and switching losses for the different types of semiconductors is given below:
I’ll also comment that Infineon has a published thermal model for the FZ400R12KE4 device. In this case they choose to model it as a separate IGBT and Diode components. The only caveat is that at the time of writing the Infineon models have the wrong file encoding (ISO-8859 instead of UTF-8) which causes PLECS to raise an error when importing the models.
