Ok, I just thought that I do not need to control the high side of an H-Bridge?
Essentially the high side needs to be on all the time(obviously the opposite side needs to be off).
i.e., if its
H1 H2
L1 L2
Then H1 is on, H2 and L1 are off, L2 is PWM.
Obviously to reverse its the opposite(H2 on, H1 and L2 off, L1 PWM).
Is this correct and good practice? For some reason I was thinking I should PWM H1 and L2 so that both would conduct at the same time but this seems to be redundant because turning off L2 should be good enough?
The problem I'm having is that if I do it discretely then its a lot of fets(or BJT's and resistors + wasted power) and I can't seem to find a driver that works with high side Pch(they all seem to want to drive Nch).
Even if it takes a few ms to charge the gate capacitance of H1 and H2 it shouldn't matter because these only occur at the start and end of powering the motor(the motor will not be reversed often). So I should be able to drive them directly from logic which will save a few transistors. The low side will just be done using cmos.
Is this a good idea or not? If not are there any mosfet drivers that will do Pch high side instead of Nch? (or is it ok to use the ones that drive Nch with Pch(I'm afraid it will pull the Pch source to far down(Although its like +-20V so I guess its not that bad but doesn't leave a lot of room))
Thanks, Jon