There’s a special, satisfying glow of accomplishment which designers feel when signing off on a high-performance, high-current (>100 A) power module such as used in PWM inverters. There are so many competing factors to be balanced and tradeoffs to be made, starting with the choice of switching frequency. For example, operation at higher frequencies enables smaller designs, but usually incurs greatly increased switching losses.
There are issues of physical construction, EMI/RFI, and thermal concerns, beyond the choice of circuit topology and frequency. Even with a well-understood basic circuit, ultimate performance is bounded by the available components. Until recently, that meant silicon-based MOSFETs and Schottky diodes, the fundamental building blocks of power modules.
That situation is changing dramatically due to emergence of fully qualified, mature devices based on silicon carbide (SiC) technology. With SiC MOSFETS and Schottky diodes, the limits which previously defined the speed-versus-efficiency tradeoff no longer apply. Instead, the new performance boundaries are pushed out so power modules can operate with very low switching losses at 5 kHz, 30 kHz, and even 100 kHz, offering greater efficiency than existing solutions but with smaller footprint and other performance advantages.
Of course, when you’re dealing with the high power and current levels, it’s not just components alone that make a successful, reliable design. Understanding the subtleties of the physical layout and thermal situation is crucial to actual performance, and that’s where a fully qualified module makes a difference.
Using power modules such as those in the ROHM “Full-SiC” series, which integrate SiC diodes and MOSFETs, removes a major block of uncertainly from of the overall power-related design mix. The reason is simple: doing so leverages lengthy experience and voluminous test data, assuring consistency in meeting target specifications along with optimal functionality and long-term reliability.