Method and apparatus switching a semiconductor switch with a multi-stage drive circuit

A multi-stage drive circuit to be coupled to a semiconductor switch having a drive terminal, a first terminal and a second terminal, to switch the semiconductor switch between on and off states, the multi-stage drive circuit comprising:

• a first drive circuit to be coupled to provide a first drive signal to the drive terminal of the semiconductor switch;
• a second drive circuit to be coupled to provide a second drive signal to the drive terminal of the semiconductor switch;
• and
• a selector circuit to be coupled to turn on the first and second drive circuits to provide the first and second drive signals to the drive terminal, respectively, wherein the selector circuit turns on the second drive circuit responsive to a current flow between the first terminal and the second terminal reaching a current threshold value, wherein the selector circuit is to be further coupled to the first terminal of the semiconductor switch to monitor a voltage between the first and second terminals, and wherein the selector circuit turns on the second drive circuit in response to the voltage between the first and second terminals of the semiconductor switch falling to a threshold value.

A multi-stage drive circuit to be coupled to a semiconductor switch having a drive terminal, a first terminal and a second terminal, to switch the semiconductor switch between on and off states, the multi-stage drive circuit comprising:

• a first drive circuit to be coupled to provide a first drive signal to the drive terminal of the semiconductor switch;
• a second drive circuit to be coupled to provide a second drive signal to the drive terminal of the semiconductor switch;
• and
• a selector circuit to be coupled to turn on the first and second drive circuits to provide the first and second drive signals to the drive terminal, respectively, wherein a voltage at the drive terminal of the semiconductor switch temporarily clamps at a first voltage level during a time that the first drive circuit is providing the first drive signal and wherein the selector circuit turns on the second drive circuit after the voltage at the drive terminal unclamps and rises from the first voltage level, wherein the selector circuit is to be further coupled to the first terminal of the semiconductor switch to monitor the voltage between the first and second terminals, and wherein the selector circuit turns on the second drive circuit responsive to the voltage between the first and second terminals falling to a threshold value indicating a time at which the voltage at the drive terminal unclamps and rises from the first voltage level.