A Quantitative Analytical Model of Paralleled SiC MOSFETs for Calculating Unbalanced Switching Currents and Energy

Uneven dynamic currents between paralleled silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (mosfets) can cause unbalanced switching losses, challenging the circuit reliability. Therefore, it is essential to quantitatively evaluate unbalanced dynamic currents during circuit design and application. However, the existing calculation methods face challenges in modeling or are time-consuming in circuits with paralleled mosfets. To address these issues, this article presents an analytical model to calculate the unbalanced switching currents and switching energy, which is applicable to circuits with any parallel number (n) and easier to use than Spice simulation method. To address the challenge of the high circuit order, the power and driving circuits are decoupled and modeled, reducing the equation order to 3n - 1. To handle the numerous parasitic mutual inductances, the inductance matrices are used for modeling. Moreover, the nonlinear die parameters and their temperature dependence are considered to guarantee accuracy. The accuracy of the presented model is verified by experiments. The model-calculated waveforms fit the tested results well. Under various switching speeds, load currents, and die temperatures, the model can accurately predict the dynamic current differences and unbalanced switching energy, with calculation errors lower than 8% for the current differences and 11% for the switching energy.