Re: Freewheeling or Generation(Motor)

Jon Slaughter wrote:

Is it common for a motor that is configured in an H-Bridge to be shorted out when it is "freewheeling"(so it no longer is freewheeling)? Does this cause the motor to loose speed slowing it down and waste power?

Basically I'm talking about what I should do with the low side mosfet when turning off the high side. If I keep it off then the motor will freewheel if I turn it on then it will I'll waste energy?

But I have to turn it off to get my mosfet drivers to work.

I guess I can flip the low side mosfet on the other side off too so the wheel isn't shorted?



normally, Hbridges have both High and Low side off during the low cycle. And in your case, you need to have the other low side on to
keep the boost cap in check in the low cycle.

You can turn on both low sides to do regenerative braking, in this case it wouldn't matter if the cap got charge or not because you're
not requested a drive current how ever, in both cases the low side
fets should come on with a low enough Ron to provide a low side path
for the boost cap. If this isn't the case then it's possible the motor
you're using is generating more REGEN energy than the low side fets can
short out.
But like I said, you should always have the driving FETS off during
the low cycle to not brake the motor and only the opposite low side to
keep the boost happy for the next on cycle..

During a slow down braking, you don't need the high side any ways so there really isn't a problem here that I can see and you'll only miss
one on cycle on restart of driving state.

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