Some power supplies and regulators don't like to have current flowing back into the output terminal. It's something I've seen casually mentioned in various answers here and it sounds reasonable enough. This has never been a problem for me until now because my designs have always had a net outflow of current, but now that I'm designing a motor controller, I need to make sure that my power supply will be able to accept potentially large transients flowing back into the supply from the flyback diodes.
Common regulators like the 7805 (not that I would use one anywhere near motor control) do not indicate a reverse current limit on their datasheets, so how do I look for a regulator that will tolerate these transients without self-destructing?
(My motor is a little 24V/35W BLDC to clarify scale.)
Best Answer
Synchronous buck regulators are pretty useful at dealing with current in reverse. After all they do it all the time if the current is discontinuous - the lower transistor has to spend a certain amount of time dragging the current backwards through the inductor. OK normally the current is all forward current but in discontinuous mode the average current could be zero.
Added bonus - you are also recovering some of the energy from the motor into the inductor.