Loss Calculation and Electrothermal Coupling

DSIM provides the function to simulate the switching transient utilizing the Piecewise Analytical Transient (PAT) model. Using the PAT model, DSIM can also calculate the power loss and junction temperature of the device. This offers a convenient approach for in-depth study of device behavior and easy comparison of devices across various manufacturers.

IGBT & SiC MOSFET Loss Calculation with DSIM

To illustrate how SiC MOSFET losses and junction temperature are calculated in DSIM, Wolfspeed’s SiC MOSFET CMF20120D (1200V, 42A) is used in a dual-active-bridge (DAB) converter example.

Build the DAB circuit as shown below:

Double-click on the 1-ph Inverter block and click the Model Level to choose the model type. In this example, SiC MOSFET is chosen as the device type. The 1-ph inverter parameter dialog and the device selection dialog are shown below.

The SiC MOSFET Module image has four nodes on the top. These nodes are the power loss nodes. The temperature at a power loss node represents the module’s case temperature, and the heat flow out of the node represents the power loss of the device.

These nodes should be connected to an external thermal circuit representing the dynamic thermal impedance between the case of the module and the ambient. In this example, Rth1 and Rth2 represent the thermal resistances between the case and the ambient.

DSIMViewer simulation results are shown in the following figure. The upper left is the simulation result of the module's case temperature. The lower left is the power loss of switch module. The upper right is the conduction, switching and total loss of the switch S1. The lower right is the junction temperature of switch Q1 and its antiparallel diode.