I am trying to understand the inductor current ramp up to steady state in a buck converter. I don't understand why the inductor current slope is not steep in the beginning. Let's say Vin=12v, Vo desired across the capacitor is 5V. Switch turns ON, Inductor current ramps up. Switch goes OFF, Inductor current starts charging the capacitor for a time interval Δt. Now the cap is charged to say, 1v. In the next cycle, the inductor current has increased, it again charges the cap for Δt. Now the cap voltage goes to 2v. This goes on. But I don't understand why the current slope becomes steeper.