The paper is devoted to the problem of uncertainty in the behavior of a pulse energy conversion system (PECS) near the bifurcation boundary. As a result of the investigations, the magnitude of the zone within which a heightened sensitivity of system dynamics varying to external and internal disturbances is revealed. Also the phenomenon of intermittency is confirmed. The validity of the results is based on an analysis of the synchronized data presented by oscillograms, bifurcation diagrams and time series, acquired on the experimental setup of DC motor drive (2 kW) with pulse-width modulation.