A power converter circuit included in a computer system magnetizes and de-magnetizes an inductor coupled to a switch node using high-side and low-side switches to alternatively couple a switch node to an input power supply node and a ground supply node. In response to detecting a drop in the voltage level of the input power supply node, the power converter circuit may adjust an on-resistance of the high-side switch to maintain performance at the lower voltage level of the input power supply node.