Kevin Parmenter, Director, Applications Engineering, Taiwan Semiconductor, NA
When I first started in the power electronics industry in the seventies, device selection was limited. We were moving from silicon bipolar transistors and rudimentary rectifiers to MOSFETs and better rectifiers. Surface-mount technology and co-packaged ICs with power devices and/or drivers were unheard of and using WBG (wide bandgap) devices was a theoretical dream. I remember finding sample parts by flipping through databooks and calling distributors to see what they might have in-stock locally and driving to pick them up or waiting for weeks for delivery. Today, designers have a choice of more power devices than ever thought possible 20 or 30 years ago.
Now, we have silicon MOSFETs. We have IGBTs, both silicon and silicon carbide MOSFETS, and we have GaN (gallium nitride) parts gaining in application usage. Rectifiers are much better than ever before and include a plethora of technologies: standard, fast, ultrafast, super-fast, highly efficient, Schottky, and trench Schottky devices. We also have silicon carbide rectifiers, mostly used in PFC (power factor correction) boost stages, and applications are expanding.
Packaging has also evolved to be almost as, or equally, important as the devices themselves. Packaging continues to improve -- not only in overall size but also in height. In the early '90s when surface-mount (SMA, SMB, SMC) packages were introduced, nobody imagined they could be improved upon. But here we are with thin SMA package mainstreaming to lower the height/thickness of products. We also have packages, such as SOD128 and other alternatives, increasing power density. These newer devices not only produce less heat and have higher efficiency in applications, but they also are able to remove that heat into the PCB much faster by using thermal heat spreaders incorporated into the packages, thus enabling end-applications to increase power density without increasing cost.
The co-packaging of devices was simply unheard of not too long ago. Now, not only do we have better power semiconductors and better discrete packaging (or no packaging, just die), we also have device combinations with functionally integrated blocks with either the controller included or driver power device partitioned to using an external controller.We also have complete power stages: just add the missing blocks and you are ready to process power. In other words, designers can add a handful of external parts, use the online tools to do the design, and they have a fully working power converter with relative ease compared to yesteryear.
In the DC-DC area, integrated point-of-load (POL) devices, complete with integrated magnetics, are available and cost effective. And even though we have access to parts for our designs that would have seemed to be out of science fiction not long ago, some things were predicted incorrectly. For instance, the demise of through-hole devices and small-signal semiconductors. They are still used for new designs daily and will be with us a long time.
What is next when it comes to device and package options? If past is prologue, I would say the possibilities are endless.