ANALYSIS OF CURRENT RUNAWAY IN A DC-DC CONVERTER WITH CURRENT-INJECTED CONTROL

The purpose of this paper is to examine the occurrence mechanism of th e current runaway phenomenon in the overcurrent limited mode of the dc -dc converter with current injected control. Taking into account the t ime delay in the turn-off instant of the switch, which is due to the d ead time and the time constant of the control circuit and the dead tim e of the switch, this phenomenon is analyzed. As a result, it is clari fied that there exist two operation modes in the overcurrent limited m ode of the dc-dc converter with current-injected control; in one mode, the current limiting characteristics are affected by only the dead ti me of the control circuit and the switch and, in the other one, both t he dead time and the time constant of the control circuit and the dead time of the switch have an effect. The current runaway phenomenon occ urs in the latter mode. The boundary condition of these two modes is d efined. Consequently, the design criterion is presented to prevent the current runaway phenomenon.