A method of controlling a tunable passive component in a pulse width modulation controlled switched mode power supply (SMPS) having a power input and an output with tunable passive component power filter. The method includes operably connecting and supplying power relative to a circuit ground to a DC bus, converting a voltage on the DC bus to an output voltage by operating a first switching device and a second switching device at a selected frequency, and filtering the output voltage with a tunable output filter, the tunable output filter including a tunable passive component responsive to a control function circuit configured to automatically tune the tunable passive component value based on a voltage associated with operation of the power supply to maintain resonance of the tunable output filter at about the selected frequency.