Electrical – Power supply over-current protection mode: constant current

power supply

I am researching power supply over-current protection modes, and I have a question about constant current.

Wikipedia claims (https://en.wikipedia.org/wiki/Foldback_(power_supply_design)) that the current remains constant while the voltage goes to zero. Doesn't this violate Ohm's Law? R is not changing, I is not changing, but somehow the voltage can change willy nilly?

What gives?

Best Answer

If you set your power supply to constant current mode, the voltage will change depending on the load. Pure Ohms law V = IR. If I is constant and you change R, V must change.

Obviously within the limits of how much V is available.

So when you set your current limit on the supply and watch the meters while you increase the load, at first V will be constant and the current needle will ramp up to the limit. After that the current needle will stay put and the voltage needle will drop.