Worst-case stability analysis of switching regulators using the structured singular value

A method to assess the effect of component tolerances on the stability of closed-loop switching regulators is given. Use of /spl mu/, the structured singular value, is made which obviates the need for time-intensive Monte Carlo simulation runs and also guarantees the assessment of the worst-case condition of the system. Furthermore, through the use of newly developed software routines for /spl mu/, the effect of up to 100 uncertainties may be taken into account. The analysis procedure entails isolating component value uncertainties /spl Delta/ from the nominal system M. Subsequent determination of /spl mu/ for this /spl Delta/-M structure enables a robustness assessment to be made for the system under study. A procedure which considers uncertainties in inductor, capacitor, and resistance values is given which enables reduction of a switching regulator system to /spl Delta/-M form. An example is given of a regulator design for which an assessment is made of the allowed component tolerances which guarantees a lower limit of the phase margin.