This models a hard-switched inductive-load turn-off (the standard "double-pulse test" used to characterize power devices), with drain/collector current held near Iload by a freewheeling diode while the device blocks the rising bus voltage. Both devices are simulated on the same shared time axis so their waveforms are directly comparable.
Voltage-rise time: t_vr = Rg·Qgd / ΔVg
Current-fall time: t_fi = Rg·Qgs2 / ΔVg
Turn-off energy: Eoff = ∫ v(t)·i(t) dt (trapezoidal, computed live)
Qgd (Miller charge) and Qgs2 are gate-charge parameters the gate driver must supply through Rg at drive swing ΔVg ≈ 18 V — a larger Rg slows the gate current and stretches both intervals, trading switching speed (and loss) for lower dv/dt and di/dt ringing.
The key material difference: a SiC MOSFET is a majority-carrier device — once the channel pinches off, current stops almost immediately. A Si IGBT is bipolar: during conduction its drift region is flooded with excess minority carriers (conductivity modulation) that cannot be removed by the gate. They must recombine, so the collector current develops a current tail:
I_tail(t) = f_tail·Iload · exp(−t / τ)
with carrier lifetime τ ≈ 100–300 ns. Because the tail current flows while v(t) is already at the full bus voltage Vdc, it dissipates energy roughly proportional to Vdc·Iload·τ — visible in the lower plot as the long gold tail on the IGBT's power curve, absent from the SiC trace. This is the dominant reason SiC power modules switch several times faster than Si IGBTs at the same voltage/current rating, enabling smaller magnetics and higher switching frequencies in EV inverters, solar inverters, and fast chargers.
- Rg — external gate resistance; higher values slow both the voltage-rise and current-fall phases for both devices.
- Iload / Vdc — the double-pulse test operating point; both scale the dissipated energy roughly linearly for each device.
- Comparison box — the percentage energy the SiC device saves versus the IGBT at the current operating point, and the raw ratio, both recomputed every time a slider moves.