Power transistor, a driver, and an overvoltage protection circuit

An electronic circuit comprising:

• a power transistor having a gate terminal, a source terminal and a drain terminal;
• a driver circuit, configured to generate an output which selectively changes a voltage at the gate terminal such that a resistance between the source terminal and the drain terminal changes in response to an input signal, and which selectively presents a high impedance to the gate terminal, wherein the driver circuit comprises a turn-off circuit configured to change the voltage on the gate terminal such that the resistance between the source terminal and the drain terminal increases, and wherein the driver circuit comprises a turn-on circuit configured to change the voltage on the gate terminal such that the resistance between the source terminal and the drain terminal decreases;
• an overvoltage protection circuit coupled to the gate terminal of the power transistor, wherein the overvoltage protection circuit is configured to generate one or more overvoltage indication signals in response to an overvoltage potential, wherein, in response to the overvoltage indication signals, the overvoltage protection circuit causes a voltage at the gate terminal to change such that the resistance between the source terminal and the drain terminal decreases, and wherein, in response to the overvoltage indication signals, the driver circuit causes the turn-off circuit to present a substantially open circuit load to the gate terminal;
• an amplifier configured to, in response to at least one of the overvoltage indication signals, cause the resistance of the power transistor between the source terminal and the drain terminal to decrease;
• and
• a comparator configured to, in response to at least one of the overvoltage indication signals, cause the turn-off circuit to present the substantially open circuit load to the gate terminal.

A method of protecting a power transistor from an overvoltage transient condition, the method comprising:

• holding a power transistor in an off state by connecting a gate of the power transistor to a source of the power transistor through a pull-down switch;
• turning on a drive switch during an overvoltage transient condition by providing a current into a gate of the drive switch through a zener diode coupled between the gate and a drain of the power transistor, the zener diode further coupled to the gate of the drive switch;
• shorting a gate of the pull-down switch to a source of the pull-down switch by a turn-on of the drive switch;
• providing a current through the zener diode into the gate of the power transistor, thereby raising a voltage at the gate of the power transistor and turning on the power transistor during the overvoltage transient condition;
• and
• discharging an overvoltage transient current through the drain to the source of the power transistor.