A new driving circuit for cascode devices performing optimal control of the storage time

In this paper several driving circuits allowing the optimal feeding of the base of a cascode device are presented. More traditional driving circuits suitable for a cascode device are efficient as long as the collector current is high and quasi constant. However in certain applications such as PFCs. where the collector current changes between zero and higher values, these driving circuits show a considerable drawback, which namely is the over-saturation of the cascode at low values of the collector current. In turn, this means a large charge in the collector and base regions of the cascode that consequently determines an increase of the device storage time. Aiming to face such a problem, a driving circuit that ensures proportional base-voltage has been proposed in order to avoid unsuitable increase of the device storage time. In other words the circuit guarantees an adequate saturation of the cascode in on-state condition and performs an excellent rejection of the voltage supply disturbances along with a high insensitivity to the parametric spreads of the drive components. The new driving circuit that implements a linear control of the base-voltage is suitable for integration.