Patent ID: 8723558

Claim:
A system for driving a bipolar junction transistor for a power converter, the system comprising: a current generator configured to output a drive current signal to the bipolar junction transistor to adjust a primary current flowing through a primary winding of a power converter; wherein the current generator is further configured to: output the drive current signal to turn on the bipolar junction transistor during a first time period, a second time period, and a third time period, the second time period separating the first time period from the third time period; drive the bipolar junction transistor to operate in a hard-saturation region during the first time period and the second time period; and drive the bipolar junction transistor to operate in a quasi-saturation region during the third time period; wherein: the first time period starts at a first time and ends at a second time; the second time period starts at a third time and ends at a fourth time; and the third time period starts at a fifth time and ends at a sixth time; wherein: the drive current signal is equal to a first current at the first time; the drive current signal is equal to a second current at the second time; the drive current signal is equal to a third current at the third time; the drive current signal is equal to a fourth current at the fourth time; the drive current signal is equal to a fifth current at the fifth time; and the drive current signal is equal to a sixth current at the sixth time; wherein: the second current is larger than the third current in magnitude; and the fourth current is larger than the fifth current in magnitude.