Tight voltage regulation of the DC Microgrid bus may lead to instability issue which leads to Microgrid system collapse. Constant Power Load (CPL) is a serious problem that exists in cascaded power electronic converters which must have a robust controller to mitigate instability issue. The controller based on mathematical model is vulnerable to model mismatch which could lead to instability especially with highly nonlinear plant. Boost converter feeding CPL is a highly nonlinear non-minimum phase system which is difficult to control based on mathematical model. In this paper a supervisory stable Fuzzy Logic Controller (SFC) based on Lyapunov theory is designed to mitigate the instability issue that is caused by the negative incremental impedance which behaves as CPL of dc boost converter. The proposed SFC is able to stabilize the output voltage of the boost converter under nominal and uncertain conditions. The proposed Controller is validated through simulation using Matlab/Simulink. To the best of the authors’ knowledge this method hasn’t been introduced before.