Buck converter

Thread Starter

jayzac

Joined Apr 24, 2009
6
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 ?

Thank you.
 

SgtWookie

Joined Jul 17, 2007
22,230
Step down WHAT voltage?

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.

http://www.smps.us has lots of good information on switching supplies.
 

Thread Starter

jayzac

Joined Apr 24, 2009
6
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 ?
 
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