Method and apparatus for high side transistor protection

1. A method for detecting a high energy event in a transistor, the method comprising:

simultaneously:

monitoring a gate to source voltage of the transistor during transistor start up; and

monitoring a timer block configured to determine when a blank time has elapsed;

continuously determining a derivative of the monitored gate to source voltage with respect to time; and

comparing the derivative of the gate to source voltage to a predetermined threshold when the blank time has elapsed:

when the derivative of the gate to source voltage exceeds the predetermined threshold:

detecting a high energy event; and

switching the transistor open; and

when the derivative of the gate source voltage does not exceed the predetermined threshold, detecting that a high energy event has not occurred.

2. The method of claim 1 , wherein the blank time is a time period for the derivative with respect to time to reflect the gate to source voltage entering a Miller Plateau region.

3. The method of claim 1 , wherein the blank time is less than a time period required for the gate to source voltage to exit a Miller Plateau region.

4. The method of claim 3 , wherein the blank time is less than half of the time period required for the gate to source voltage to exit a Miller Plateau region.

5. The method of claim 1 , wherein monitoring the gate to source voltage of the transistor during transistor start up and determining a derivative of the monitored gate to source voltage with respect to time are performed by a hardware differentiator.

6. The method of claim 5 , wherein the hardware differentiator is an Op-Amp differentiator.

7. The method of claim 1 , wherein monitoring the gate to source voltage of the transistor during transistor start up is performed by a voltage probe and determining the derivative of the monitored gate to source voltage with respect to time is performed by a software differentiator.

8. The method of claim 1 , wherein monitoring the gate to source voltage of the transistor during transistor start up comprises monitoring a metal-oxide semiconductor field effect transistor (MOSFET).

9. The method of claim 8 , wherein the MOSFET is a high side transistor inside an electrical control unit.

10. The method of claim 8 , wherein the MOSFET is in a direct injection driver for a powertrain electrical control unit.

11. A transistor protection circuit comprising:

a transistor including a gate node, a source node, and a drain node;

a controller having a controller output connected to the gate node of the transistor, the controller configured to switch the transistor on;

a differentiator connected to the gate node at a first input and the source node at a second input, wherein the differentiator has a differential output of a derivative of the gate to source voltage;

a timer block connected to the differential output and to the controller output, the timer block includes a control scheme, wherein after an initial blank time has elapsed, the control scheme is operable to cause the timer block to:

detect a high energy event when the derivative of the gate to source voltage exceeds a predetermined threshold; and

fail to detect a high energy event when the derivative of the gate to source voltage does not exceed the predetermined threshold.

12. The transistor protection circuit of claim 11 , wherein the initial blank time is a time required for the differential output to reflect a gate to source voltage of the transistor entering a Miller Plateau region.

13. The transistor protection circuit of claim 12 , wherein the blank time is less than a time required for the gate to source voltage of the transistor to exit the Miller Plateau region.

14. The transistor protection circuit of claim 13 , wherein the blank time is at least 50% shorter than the time required for the gate to source voltage of the transistor to exit the Miller Plateau region.

15. The transistor protection circuit of claim 14 , wherein the transistor is a metal oxide semiconductor field effect transistor (MOSFET).

16. The transistor protection circuit of claim 11 , wherein the transistor is a high side input transistor for an electrical control unit.

17. The transistor protection circuit of claim 16 , wherein the transistor is in a direct injection driver in a powertrain electrical control unit.

18. A method for detecting a high energy event in a transistor, the method comprising:

simultaneously:

monitoring a gate to source voltage of a transistor during transistor start up;

monitoring a timer block configured to determine when a blank time has elapsed;

continuously determining a derivative of the monitored gate to source voltage with respect to time;

detecting a high energy event when the derivative of the gate to source voltage exceeds a predetermined threshold, the high energy event being detected as a result of the derivative of the gate to source voltage exceeding the predetermined threshold;

detecting that a high energy event has not occurred when the derivative of the gate to source voltage fails to exceed the predetermined threshold; and

switching the transistor open when the high energy event is detected.