Power Integrations, Inc.
BJT driver with dynamic adjustment of storage time versus input line voltage variations

Abstract:

A method of dynamically adjusting a storage time of a bipolar junction transistor (BJT) in a switched mode power converter during a switching cycle includes generating a storage time reference signal responsive to an input voltage signal. A collector off signal is generated responsive to a comparison of a current sense signal to a collector off reference threshold signal. The current sense signal is representative of a switch current of the BJT. A base off reference threshold signal is generated responsive to the storage time reference signal and the collector off signal. A base off signal is generated responsive to a comparison of the current sense signal and the base off reference threshold signal. Charging of a base terminal of the BJT is discontinued responsive to the base off signal, and the base terminal of the BJT is discharged responsive to the collector off signal.