Power transistor driving circuits and methods for switching mode power supplies

A method for turning off a first bipolar transistor, comprising:

• coupling an MOS transistor to a base of the first bipolar transistor;
• during a first time period in response to a first control signal, applying a first voltage to a gate of the MOS transistor to discharge the first bipolar transistor;
• and
• during a second time period in response to a second control signal, applying a second voltage to the gate of the MOS transistor to discharge the first bipolar transistor, the second voltage being lower than the first voltage.

A driver circuit for turning off a first bipolar transistor, the driver circuit comprising:

• a current mirror having first and second PMOS transistors;
• a second bipolar transistor coupled to the second PMOS transistor of the current mirror;
• a plurality of diode devices coupled in series between a collector and a base of the second bipolar transistor;
• and
• a first MOS transistor having a gate terminal coupled to the collector of the second bipolar transistor and a drain terminal for coupling to a control terminal of the first bipolar transistor for turning off the first bipolar transistor.