How to prevent regenerative power from destroying my DC motor controller

Question

I have a DC motor controller that clearly says to use a battery and not to run it from a power supply because of the likelyhood of the regenerative power damaging the controller.

Unfortunately, this is not an option for me as I have to use a power supply and not have a battery to place in parallel to absorb the excess energy.

If I use a reverse biased diode would that prevent the regenerative power from damaging the controller? If so how do I implement it correctly or is there better method?

Also, there would never be a situation where the power to the 12V BLDC motor would be abruptly terminated, as it would always be slowly powered down. If that is the case, do I even need to be concerned about the regenerative power damaging the controller?

Answer 1

In the absence of a battery, you need to dump the regenerated power in a braking resistor.

Many controllers have an output signal indicating when regeneration is occuring, and this can be used to drive the gate of a suitably sized MOSFET connecting a low value high power resistor across the supply.

In the absence of this signal, you need to generate your own regeneration signal.

To do this, find how much voltage rise the supply can tolerate before going into error state, then setup a voltage comparator to test for when the supply rises to below this level, but above the normal output voltage. The output should then be used to switch the braking resistor MOSFET (as above).

A simpler alternative, for low power levels, is a power Zener, selected to be above the normal range of the supply, but below the trip voltage.

Answer 2

Energy always has to go somewhere. It can not be stopped or destroyed (or created from scratch). The amount of regenerative energy will depend on the mass/inertia of the mechanical parts that the motor drives. You have not specified how large the motor is and what it drives. A propeller will probably be light, a conveyor belt with lots of stuff on it will be heavy.

A battery can accept the regenerative energy, it will just charge itself, but a power supply may not. It will just pump the supply rails until something blows up. What you really need is a dynamic brake - a resistor with large enough power rating and some mechanism that will switch it in and out (a simple voltage comparator + FET can do.)