Abstract: A step-down switching mode power supply having: a Buck converter configured to provide power to a load, wherein the Buck converter has a power switch and an energy storage component; a current sense circuit coupled to the power switch to generate a current sense signal; a square circuit configured to generate a first multiply signal indicating the squared value of the input voltage; a multiply circuit configured to generate a product signal based on the first multiply signal and a second multiply signal; a current comparison circuit configured to generate a current comparison signal based on the current sense signal and the product signal; and a logic circuit configured to control the power switch.