The charge pump circuit is mounted onto a strip of prototyping board ready for attaching to the MPPT Solar Charge Controller test rig. It's producing about 9v above the battery voltage which will be used to drive the gate of the high side MOSFETs.
By Julian
Youtuber, shed dweller, solar charge controller aficionado
Yeah, I like to have a common -ve in my setup, since I have so many different battery banks and sub-circuits..! hehe I have come up with a really simple circuit to convert a -ve switching controller to a +ve one & increase it's capacity to boot! 🙂 I should send you the schematic, could be useful. Tbh I have never actually used a P-Channel for anything, but yeah I understand they have a higher on-resistance. But I would presume that is only relatively speaking and may not be a real issue.
Same here. The really cheap controllers all seem to switch the negative side, but fail to mention that in the instruction manual. So you wire up a common negative and short out all the controller's switching functions!
From what I've read, P-channel FETs don't have the low on resistance of N-channel types.
High side and low side FET circuits are worthy of their own video – thanks for the idea.
I think it's a good design principle to keep the battery in the low side like you a doing. A lot ov charge controllers use a mosfet and just simply put the battery in the drain circuit. While this works perfectly well, it's a problem if you want a common negative between your panels and your battery. You could also try a Pchannel as the switch then you would only need to switch the gate to ground, and not require any boost voltage.
Yes, exactly that. To switch on fully, the MOSFET gate needs to be 9 volts higher than source, but the source pin is connected to battery positive. Regardless of actual battery voltage (which varies considerably), the charge pump output is always battery positive plus 9 volts.
Just curious why you need so much voltage to turn on the mosfet? Is it because you've got the battery in the source circuit and would need to get the gate up much higher than the battery?