Systems and methods for driving bipolar transistors related to power converters

A controller for a power converter, the controller comprising:

• a first controller terminal connected to a first base of a first bipolar transistor, the first bipolar transistor further including a first collector and a first emitter;
• a second controller terminal connected to the first emitter of the first bipolar transistor and a second base of a second bipolar transistor, the second bipolar transistor further including a second collector and a second emitter, the second collector being connected to the first collector;
• and
• a third controller terminal connected to the second emitter of the second bipolar transistor and a resistor, the resistor being configured to generate a sensing voltage received by the third controller terminal;
• wherein:
• if the sensing voltage is smaller than a predetermined threshold, the first controller terminal is configured to output a first current to the first base to generate a second current at the first emitter, the second current flowing to the second base to turn on the second bipolar transistor;
• and
• if the sensing voltage reaches the predetermined threshold, the second controller terminal is configured to output a third current to the second base before the second bipolar transistor becomes turned off;
• wherein the third current is smaller than the second current in magnitude.