The Virtual Frontier: Advanced Simulation in Power Electronics Design

Wide Bandgap - a High Power Enabler

In higher power designs, the electronics sector is witnessing a transition from silicon to wide bandgap (WBG) semiconductors, such as silicon carbide (SiC) and gallium nitride (GaN). In these designs, conventional SPICE modelling techniques are barely used. The reason for this is that they can be computationally expensive and slow, and are unable to provide an accurate indication of losses and thermals (at device junction and system level) that are both more serious concerns in high-power circuits. Instead, Piecewise Linear Electrical Circuit Simulation (PLECS) is the simulator of choice due its ability to model these characteristics.

PLECS uses ideal switches and lookup tables for losses, balancing accuracy and simulation speed. However, because the losses and thermal models use typical datasheet values, it is important for some design margin to be factored in.

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The Promise of Digital in Power Electronics

The integration of advanced simulation tools in power electronics design is not just enhancing current capabilities but is also paving the way for future innovations. Power electronic design is, per se, always interdisciplinary, because there are electronics, thermals, mechanics and control systems that play into one design.

With PLECS modelling, it is possible to have a suitable estimation of the losses of the parts that are used in the design. The data that is coming out of this simulation step can then be used to estimate thermal needs for the design. Various gas and liquid flow simulation tools can help to estimate how the heatsink needs to be formed and predict the needed gas or liquid flow to have the temperature in the right window over all the possible load cases of the electronics.

Once that is done, further mechanical studies can be completed with FEM, which is often necessary (especially in vehicle applications) because the case that holds the power electronics is also a stressed member of the frame, which brings even more difficulties.

With electronics, thermals and mechanics covered, one piece of the puzzle is left -- the control side of things. Here, digital technology helps in the form of hardware-in-the-loop test stations, which mimic the hardware for the control system of choice. This means that a control algorithm can be programmed in software on a µC or µP, and the test stand will then mimic the hardware that has been chosen.

This enables engineering teams to work in parallel instead of solving tasks one after another. With HIL test stations, a change of parts is just a parameter change for the test stand, and a prototype rebuild is needed.