Kevin Parmenter, Field Applications Manger, Taiwan Semiconductor
The promise of wide bandgap semiconductors (WBG) are higher switching frequency and higher operating temperatures perhaps smaller sizes, greater efficiencies and perhaps higher reliability, less size, less cooling – no fans for example, smaller heatsinks, smaller capacitors, less weight and overall better performance than Silicon power devices. Passive components from heat sinks, capacitors and coils get smaller. “SWAP” gets better yet there are challenges. None of the benefits comes by simply dropping in a GaN device and instantly better performance occurs. Many other technologies must come into play such as packaging. How do you package a power device that switches in 1-5 nanoseconds – the di/dt and dv/dt are off the charts. This has caused innovations in packaging all the way from no package at all to complete co-packaged and tested ready to go topologies which contain the gate drivers and all or part of the rest of the system. You must drop parasitic capacitance and inductance which will impact performance.
Our industry always wants to make advances one new product at time yet usually this is never the case. For something new and revolutionary to be applied it requires something else to be developed or refined to suit the new devices in the case of new topologies using GaN such as bridgeless totem pole stages for example, digital controllers (once the other orphan that we said we would never use) must be used. Why – because its perfect for this purpose and no one size fits all analog bridgeless totem pole controller is available so digital control to the rescue designers can get precisely what they need – it’s a symbiotic relationship Digital control thrives and shines WBG devices in many cases need digital control to realize benefits. Digital control took about 10 years from introduction until practical implementation. Some of the GaN suppliers have achieved AEC-Q automotive qualification levels and other than space rated radiation resistance testing (which wide bandgap devices are also better at than silicon) its as good as it gets. If you can pass an AEC-Q qualification you can pass almost anything else from a qualification standpoint. The packages (or devices with no packages) are also passing these qualifications. Slowly the objections of the pundits and hold outs are falling one by one. About the time someone says it can’t be done someone knocks down another barrier. What remains? I believe we will see more packaging innovation including more co-packaging of complete stages with higher and higher levels of integration and power levels.
At APEC this year I will host a rap session on when will the devices catch up with magnetics. https://www.apec-conf.org/rapsessions (in fact all the sessions this year involve mainstreaming WBG devices in some fashion) We say we must have magnetics breakthroughs and innovation to realize the potential of wide bandgap switches, but do we? If so, specifically what? The IC devices must catch up to GaN discretes and I believe and having improved measurement equipment including probes available and to analyze the designs correctly will be key. The power electronics design community is once again knocking down the obstacles and making the impossible or improbable common applications – this is what we do.