Dynamic IGBT gate drive to reduce switching loss
A vehicle includes an electric machine, an IGBT, and a gate driver. The IGBT has a gate, an emitter, and a collector and is configured to flow an electric charge through a phase of the electric machine. The gate driver is configured to flow current onto the gate at a first level, and in response to a time integral of a voltage across the phase exceeding a predetermined level, transition from the first level to a second level less than the first level.
1. A vehicle comprising:
an electric machine;
an IGBT having a gate, an emitter, and a collector, configured to flow an electric charge through a phase of the electric machine; and
a gate driver configured to flow current onto the gate at a first level, and in response to a time integral of a voltage across the phase exceeding a predetermined level, transition from the first level to a second level less than the first level.
2. The vehicle of claim 1 , wherein the predetermined level is based on an electric potential of the electric charge.
3. The vehicle of claim 1 , wherein the first level is based on a gate capacitance of the IGBT, and an electric potential of the electric charge.
4. The vehicle of claim 1 further comprising a freewheeling diode coupled anti-parallel with the IGBT, wherein the predetermined level is derived from an electric potential of the electric charge such that an overshoot voltage across the freewheeling diode does not exceed a diode limit.
5. The vehicle of claim 4 , wherein the second level is based on a rate of change of collector current of the IGBT such that a maximum diode voltage does not exceed a breakdown threshold.
6. The vehicle of claim 1 , wherein the time integral is for a period beginning when the gate driver receives an IGBT turn-on signal and ending when the gate driver turns off the IGBT.
7. The vehicle of claim 1 , wherein the first level is based on a parasitic inductance associated with the gate of the IGBT, and a temperature of the IGBT.
8. A method of controlling an IGBT of a power system comprising:
by a gate driver, flowing a current at a first level onto a gate of an IGBT; and
in response to a time integral of a voltage across the IGBT exceeding a predetermined threshold, transitioning the current from the first level to a second level less than the first level.
9. The method of claim 8 , wherein the first level is based on a gate capacitance of the IGBT.
10. The method of claim 8 , wherein the second level is based on a rate of change of collector current of the IGBT such that a reverse bias diode voltage across a freewheeling diode, coupled anti-parallel with the IGBT, does not exceed a breakdown threshold.
11. The method of claim 8 , wherein the time integral is for a period beginning when the gate driver receives an IGBT turn-on signal and ending when the gate driver turns off the IGBT.
12. The method of claim 8 , wherein the predetermined threshold is derived from an electric potential associated with the current such that an overshoot voltage across a freewheeling diode coupled anti-parallel with the IGBT does not exceed a diode limit.
13. A vehicle powertrain comprising:
an IGBT having a gate, an emitter and a collector; and
a gate driver configured to flow current onto the gate at a first level, and in response to a time integral of resulting collector to emitter voltage exceeding a predetermined level, transition from the first level to a second level less than the first level.
14. The vehicle powertrain of claim 13 , wherein the first level is based on a gate capacitance of the IGBT and a parasitic inductance of the IGBT.
15. The vehicle powertrain of claim 13 further comprising a freewheeling diode coupled anti-parallel with the IGBT, wherein the predetermined level is derived from a voltage associated with the current such that an overshoot voltage across the freewheeling diode does not exceed a diode limit.
16. The vehicle powertrain of claim 15 , wherein the second level is based on a rate of change of collector current of the IGBT such that a maximum diode voltage does not exceed a breakdown threshold.
17. The vehicle powertrain of claim 13 , wherein the time integral is for a period beginning when the gate driver receives an IGBT turn-on signal and ending when the gate driver turns off the IGBT.
18. The vehicle powertrain of claim 13 , wherein the first level is based on a parasitic inductance associated with the gate of the IGBT, and a temperature of the IGBT.