A lossless inductor current sense technique integrates a matched, tunable complimentary filter with a switch mode power supply (SMPS) controller for accurately measuring current through the power inductor of the SMPS without introducing losses in the power circuit. The complimentary filter can be adjusted in-circuit to significantly reduce the effects of component tolerances, accurately measuring the power inductor current for over current protection and/or closed loop control. The frequency pole and gain of the complimentary integrated filter can be adjusted on the fly in order to adapt to dynamically changing operating conditions of the SMPS system.