I have a DCDC Buck-Boost converter circuit that needs inrush protection. I have looked around the internet and the resources for a viable solution and decided to use the following circuit from this answer to a similar question. My circuit is:
The input is 9-36V DC and the current may vary between a wide range of 0.5A and ~3.5A (different modes of operation). I have simulated this circuit with a MOS that was available in LTspice though I am planning on buying a different one.
What I am worried about is the SOA's of the MOSFET's. Most FET's declare a drain current that seems suitable for my application, however the MOS will be fully on after it limits the inrush current. This will make the Vds fairly small and that leaves my operating current levels outside of the SOA's.
How should I approach this situation? I believe the SOA's are to be trusted and I may destroy my MOS if I operate it fully on with such high currents but there might be something I am missing because inrush limiting in DCDC converters is not something new.
Extra question for those interested: PMOS in my case is normally on in the simulation since its Vg is slightly less than its Vs (I think). This causes a small inrush leak. The MOS instantly turns off and slowly opens with the help of the feedback capacitor C15 and the turning on of Q1. Does this make sense or is it something that happens in a simulation environment?
Edit: The load can be approximated to a parallel RC with R = 45-50ohms and C = 270-300uF. The converter has a soft-start capability and I can be flexible with it. Right now, it is set to around 30ms. The main part or the inrush that I am observing happens between 1.2-3ms. The input of the DC-DC block also has a 3rd order EMI filter. The capacitance of it is included in the approximation but the inductance is not. It is around 7.3uH.
Thanks in advance for your attention and answers!
Arbitrary PMOS SOA example: https://www.infineon.com/dgdl/SPD09P06PL+Rev2.5.pdf?folderId=db3a30431ed1d7b2011f4042f2ff4ec5&fileId=db3a30431ed1d7b2011f40486c6a4ed4