Quote Originally Posted by dobrodewed View Post
does anyone have a schematic for a A3979 driver pwb?
Question: is there anyway to use the outputs to the motors from the A3979s to drive an additional higher output h-bridge. My controller works well, it's just under powered. I'm thinking of it as a preamp. All the signal shapes are correct, so just amplify them? Power these new h-bridges with the new 48v as well and voila I can drive bigger motors
I don't think that just putting a power driver stage on the end will work because the chip (A3979) has sense inputs that detect the current the motor is taking and adjusts parameters to suit as it is driving the motor. You will need to look at the data sheet and work out what this sense voltage does and then figure out a way to derive it from your power driver output using suitable resistors in series with the windings. This is the way the chip controls the current in the windings. The sense voltage should not exceed 0.5v and so the resistor in series with your windings needs to take account of this. Also the reference voltage applied to the chip will change the current in the windings so this too has to be considered.

Basically it is not as simple as just adding a power stage driver, but I think it could be done.

Good luck and please post any results you get.