A transient prediction and stability analysis tool for DC-DC converters

An Excel-based tool that calculates both the output voltage deviation V/sub max/ due to load transients as well as small-signal stability characteristics of a DC-DC converter is presented. Using a macromodel of the converter, the tool calculates and plots the voltage loop gain characteristics of a DC-DC converter for a wide variety of load networks and voltage-sense methods. The tool also predicts stability margins of the converter+load combination and estimates the under/overshoot of the regulated output voltage due to a given load transient. The method used is unique in the sense that 1) it decouples the closed loop system into converter-only and load-only subsystems which allows a very convenient way of calculating loop response when the load is varied; and 2) the converter-only subsystem can be characterized by measured data which yields a very accurate prediction of the loop response, and hence the stability margin. The transient response of the converter is estimated by mapping the closed-loop system to a second order parallel RLC network and analytically deriving the response of the RLC network. The purpose of the tool is to enable the converter user to get an accurate estimate of stability margins and transient response of the module in an application without actually making measurements.