Hi,
I am designing a buck converter to step down the voltage down to 12V. What is the difference in choosing the power transistor between pmos and nmos for this design ?
If it's mains powered, the output must be isolated from mains power by coupled inductors (ie: transformer).
For buck-type designs, N-ch MOSFETs require a high-side driver. P-ch MOSFETs don't; but their gate charge is ~2.5 times higher than that of an equivalent N-ch MOSFET. This means the gate drive needs to be considerably "beefier" than that of an N-ch, otherwise high power dissipation in the MOSFET will result.
The design is to step down 20W solar panel of Vpp about 18V to 12V. So the pmos is applicable in this design by just using a normal npn transistor to drive the pmos ?