I need to connect a 12S LiPo (50.4V fully charged) to a power bus. This bus has over 6,000uF of capacitance on it and can be at higher voltage than the battery itself. Ideally this would be done as quickly as possible, in the 1-2 mS range. The switch needs to support about 300w steady state.
I currently have an Hbridge driver abused into making an isolated 10v for an isolated gate driver.
The attached circuit has been my most robust thus far but only stays working when the turn on time is up in the 200+ ms range. When I reduce the gate resistance and capacitor to the shown values it turns on in ~32ms on the bench. Then when connect to the battery and about half the capacitance is still works. But when finally connected to the full level of capacitance it fails instantly (FETs short and stay closed). I'm really confused because the measured inrush current is FAR below the rated amount for the FETs, I have tried P ch, Nch, IGBTs, GaN everything. It does get more robust as the FETs current capacity goes up but nothing has just worked. I have looked for dedicated current controlled drivers but haven't found one that works with a bidirectional switch AND at these voltage levels.
I have killed A LOT of silicon trying to get this working and i'm at my wits end, I would really apricate any advice. Maybe I need to be turning the FETs on faster not slower?
FET PN: AUIRF7749L2TR
Driver PN: ADUM4121-1ARIZ-RL
Hbridge driver for the isolated 10v: MAX13256ATB+T
10v LDO: S-1142BA0I-E6T1U