02 | Keysight | Power Electronics Device Modeling - Technical Overview

Power Electronics Device Modeling

Power Electronics (PE) design engineers are under strong schedule pressure to address the

growing needs of power conversion, motor drivers, etc. Meanwhile, to enable smaller designs,

the switching frequencies are going up into the 100s of kHz and even low MHz. While these

might be modest frequencies, the voltages, and in particular, the changes in voltages versus

time (dV/dt) are very large. GaN devices today are switching within 250 ps, generating

harmonic content into the GHz range. Inductances as small as 0.1 nH can reshape the

waveforms driving the gate, causing ringing and transient induced noise. Stray inductance in

the high current path is very common, leading to large L*di/dt.

These surges in voltage and current, along with the ringing that follows can cause circuit

malfunction, and in some cases, circuit explosion. The high switching frequencies and

associated harmonics lead to undesirable electromagnetic interference.

These are big problems that need to be simulated and resolved. On the one hand, designers

may improve reliability by using larger power modules, but this leads to increased cost and size.

On the other hand, smaller nimbler devices must be simulated to predict voltage and current

surge issues. Modern power converters are now increasingly digitally controlled, with arrays of

discrete power devices placed side-by-side. To capture a transient over-voltage of a device, the

question arises: “How can we model this?”

Many PE designers simply give up, relying instead on their decades of experience making

circuits work on the lab bench. Designs are therefore iterative, with managers planning small

changes between hardware releases. R&D budgets can swell due to longer than expected

design cycles. Even worse, the design team loses its edge on the competition.

4.5 4.6 4.7 4.8 4.9

5.1 5.2 5.3 5.4 5.5

Time (µSec)

-5

Volts

Time Domain Measurements on Half-Bridge Circuit with SiC MOSFETs

Low gate drive

High gate drive

Half-bridge midpoint/40

Inductor current

Amps

Voltage

Temperature