Solar PWM Charging Mosfet Selection

Thread Starter


Joined Mar 19, 2016
Hello Guys.

I am making a Solar Charge Controller with PWM. For PWM, I need to connect the MOSFET to the high side so as to control the current going into the battery from the panel.

If I connect an N channel MOSFET, that would need a charge pump to increase the gate voltage above the Vdd.
But if I use a P channel MOSFET, that would not be necessity, since I only need to turn off the gate supply for the MOSFET to conduct and vice versa.

Some of the examples on the net have used N channel with a charge pump and I really dont understand why they have not used a P channel MOSFET instead.

What would be a better selection in terms of efficiency and power dissipation.




Joined Aug 21, 2008
Your observation are valid. I would go with a P-channel MOSFET.

The N-Channel MOSFET in the circuit above can be replaced with a diode, but at slightly lower efficiency.

Thread Starter


Joined Mar 19, 2016
Hi DC,

Thanks for the reply. Ideally, I would want the drop to be "0", but putting a N Mosfet instead of the diode, will again require a gate drive circuitry, won't it?

Also can you please share the buck converter calculations?



Joined May 19, 2014
@DickCappels @sonar_abhi

Dick, I think Sonar is talking about a non-inductor based simple PWM charge controller, not a power converter.

Sonar, "Charge Controllers" may be cheap and easy to build but they are not efficient. Dick is talking about a power converter, which is very efficient compared to a charge controller.

What is your application?