I've come across a circuit that has a diode in parallel with a power switch that's controlling a BLDC motor circuit. I was told that it's a flyback diode to prevent voltage spikes from an inductive load, but that doesn't really make sense to me. I've always seen a flyback diode placed in parallel with an inductive load, like with a relay coil, or in a buck converter. The two ways I understand it are that:
a) the diode provides a path for the current in the inductive load to continue to flow
b) when the current though the inductive load is suddenly stopped, the voltage, which is V=L*di/dt is a very large negative number, so V_LOAD goes negative. However the diode is then forward biased, so it clamps V_LOAD at the forward voltage of the diode
With the circuit in question, neither of those conditions hold true. The current could have to instantly change direction for the diode to conduct (which would probably cause a lot of other issues), and V_LOAD would have to increase in voltage in order for diode to be forward biased.
Has anyone seen this before and know what the purpose of this diode is? It kind of seems like someone didn't know what they were doing by putting the diode in that position, but I might be missing something super obvious.
