Hall current sensors are excellent but a bit costly and greedy on power. They are probably justified to save all the hassle of using opto isolators with op amps and opto feedback.
Flux[ Parent ]
The pick up coil solution is complicated by the fact that it misses the constant current portion of the signal, like a transformer would. If the current reliably dropped to zero at some point in the buck cycle, you could use that to rezero the sensor, but that isn't generally the case for bucks.
A Hall sensor or "going naked" might be your best bet.[ Parent ]
