As the motor brakes, the kinetic energy stored into the load (the bigger the system inertia, the higher the energy) will flow back to the power supply through the drive (as our drive is a 4-quadrant one, which allows this to happen).

Usually the power supply cannot accept this energy, acting as a wall causing the voltage to increase (the voltage from the supply now adds to the backEMF created by the motor).

If the amount of energy is small, there might not even be any increase in voltage, as the drive can accumulate this energy into its capacitors — if the energy is too high, then the over voltage protection of the drive will trigger, thus disabling the PWM outputs of the drive. This will reduce the voltage, but at the same time will stop the braking process, and the load will decelerate freely due to the frictions in the system.

If you are using a rechargeable battery to power the drive, then the battery will accept this energy and will in fact be recharged during the braking. Make sure not to brake on a fully charged battery, as while most lead-acid accumulators support over-charging, this will shorten their life time.

To avoid the drive being disabled during braking, when the energy is simply too much for the drive to handle, we provide a simple solution: evacuate this surplus of energy on a braking resistor as heat.

“Activate if power supply > xx V” means that the drive will open the “evacuation valve”, in our case a transistor, and redirect the energy to the resistor to be dissipated, when the voltage it sees on the +Vmot pin is higher than the value set in the software. As soon as the voltage drops below this value the transistor will be closed, to avoid wasting the energy from the power supply.