Thanks for your suggestion I will keep it in mind. So for the sake of learning, when the MOSFET switches off, the magnetic field of the coil collapses, and current flows through the diode, and all is sweet? Or not?
In a typical (non-synchronous buck converter):
- high side switch turned on
- current flows through high side switch (MOSFET)
- current flows through inductor
- current flows through output capacitor (charging it)
- high side switch turned off
- current flows through inductor
- current flows through output capacitor (discharging it)
- current flows through buck diode
What exactly is the problem with this? Are you saying high voltage will appear at the inductor/PMOS node which will destroy the MOSFET?
No, it probably won't destroy the MOSFET, but it won't work as an electronic load. It will be a dead short to your device under test.
Could high speed opamps cure problem with phase shifts?
Possibly, but I would think high speed op amps could introduce even more problems (noise sensitivity and higher frequency oscillations being some.) The chip is compensated (stabilised) for a few particular configurations - operating it outside of this range can lead to anything happening.