Hello EPCer,
How to consideration design for SGT MOSFET and GaN FET in ACF / LLC SR?
Hello,
EPC GaN FET work very well in SR applications. They offer the lowest Rds(on) per area so you can achieve high power density. The low Qg also means that gate losses are reduced to improve efficiency at light load and high switching frequencies, and it also makes it easier to parallel them in high power applications. The top side cooling of the EPC GaN FET also allows very effective cooling, again for higher power density.
Since the devices are so efficient in the higher voltage classes, it is also possible to replace a 4 FET full-bridge rectifier topology with a 2 FET center tap solution.
We have a video that also discusses SR LLC applications here: Why GaN 05 - AC/DC PFC and Synchronous Rectification (epc-co.com) (start at 5:12)
In these applications you should pay attention to difference between Si and GaN in the 3rd quadrant operation. For example, GaN FETs do not have reverse recovery, and its reverse conduction characteristic has a higher voltage drop than Si with should be managed by using a small enough deadtime. This article bp_2018_06.pdf (epc-co.com) covers this topic in much detail.