Multimode base drive circuit for power switching transistor

摘要

A base drive circuit for a power switching transistor in a power inverter circuit utilizes a center tapped current transformer winding to regeneratively couple the collector current of the power switching transistor to its base drive electrode. A first segment of the center tapped transformer winding is coupled via a control transistor to provide proportional base drive to the power transistors when it is biased into conduction. This forward drive mode continues until the control transistor is biased nonconducting, at which point, the second segment of the center tapped transformer winding is connected to the base drive electrode to provide a reverse drive current to the power transistor base to provide rapid turn-off and reset the transformer. A supplemental drive path coupled to a converter power source via a diode to the control transistor operates to supply additional drive current therethrough to the power transistor at the turn-on transition in order to eliminate the quasi-saturation region that normally exists in a regeneratively driven power switching transistor at turn-on.