System and method for monitoring in real time the operating state of an IGBT device

1. A system for determining at least one of a junction temperature and a remaining lifetime of an IGBT device, comprising:

a differential unit configured to receive a gate-emitter voltage characteristic of the IGBT device to be measured, and to differentiate the gate-emitter voltage characteristic to obtain pulses correlating with edges formed by a Miller plateau phase during a switch-off phase of the IGBT device;

a timer unit configured to measure a time delay between the obtained pulses indicating a start and end of the Miller plateau phase during the switch-off phase of the IGBT device; and

a junction temperature calculation unit configured to determine at least one of the junction temperature and the remaining lifetime of the IGBT device based on the measured time delay.

2. The system according to claim 1 , comprising:

a signal amplitude detector unit and a comparator unit configured to select the pulses indicating the start and end of the Miller plateau phase during the switch-off phase of the IGBT device from other pulses,

wherein the comparator unit is configured to filter pulses based on a reference switch voltage as a threshold level, and

wherein the signal amplitude detection unit is configured to generate the respective threshold levels based on the amplitudes of the pulses obtained in the differential unit.

3. The system according to claim 1 , comprising:

a signal amplitude detector unit and a comparator unit configured to select the pulses indicating the start and end of the Miller plateau phase during the switch-off phase of the IGBT device from other pulses,

wherein the comparator unit is configured to compare voltage levels of pulses with a respective reference switch voltage as a threshold level to obtain binary pulse signals, and

wherein the signal amplitude detector unit is configured to generate the respective threshold levels based on the amplitudes of the pulses obtained in the differential unit.

4. The system according to claim 3 , wherein the comparator unit is configured to apply a hysteresis when comparing the voltage levels of pulses with the respective reference switch voltage as a threshold level to obtain the binary pulse signals.

5. The system according to claim 1 , wherein the junction temperature calculation unit is configured to determine the junction temperature of the IGBT device based on the measured time delay and on a collector-emitter voltage of the IGBT device and an IGBT device current.

6. The system according to claim 5 , comprising:

a signal amplitude detector unit and a comparator unit configured to select the pulses indicating the start and end of the Miller plateau phase during the switch-off phase of the IGBT device from other pulses,

wherein the comparator unit is configured to filter pulses based on a reference switch voltage as a threshold level, and

wherein the signal amplitude detection unit is configured to generate the respective threshold levels based on the amplitudes of the pulses obtained in the differential unit.

7. The system according to claim 5 , comprising:

a signal amplitude detector unit and a comparator unit configured to select the pulses indicating the start and end of the Miller plateau phase during the switch-off phase of the IGBT device from other pulses,

wherein the comparator unit is configured to compare voltage levels of pulses with a respective reference switch voltage as a threshold level to obtain binary pulse signals, and

wherein the signal amplitude detector unit is configured to generate the respective threshold levels based on the amplitudes of the pulses obtained in the differential unit.

8. The system according to claim 7 , wherein the comparator unit is configured to apply a hysteresis when comparing the voltage levels of pulses with the respective reference switch voltage as a threshold level to obtain the binary pulse signals.

9. The system according to claim 5 , wherein the junction temperature calculation unit is configured to determine at least one of the junction temperature of the IGBT device and an indication of the remaining lifetime by means of at least one of a look-up table and a mathematical function.

10. The system according to claim 9 , comprising:

a signal amplitude detector unit and a comparator unit configured to select the pulses indicating the start and end of the Miller plateau phase during the switch-off phase of the IGBT device from other pulses,

wherein the comparator unit is configured to filter pulses based on a reference switch voltage as a threshold level, and

wherein the signal amplitude detection unit is configured to generate the respective threshold levels based on the amplitudes of the pulses obtained in the differential unit.

11. The system according to claim 9 , comprising:

a signal amplitude detector unit and a comparator unit configured to select the pulses indicating the start and end of the Miller plateau phase during the switch-off phase of the IGBT device from other pulses,

wherein the comparator unit is configured to compare voltage levels of pulses with a respective reference switch voltage as a threshold level to obtain binary pulse signals, and

wherein the signal amplitude detector unit is configured to generate the respective threshold levels based on the amplitudes of the pulses obtained in the differential unit.

12. The system according to claim 11 , wherein the comparator unit is configured to apply a hysteresis when comparing the voltage levels of pulses with the respective reference switch voltage as a threshold level to obtain the binary pulse signals.

13. A method for determining at least one of a junction temperature and a remaining lifetime of an IGBT device, the method comprising:

differentiating a gate-emitter voltage characteristic to obtain pulses correlating with edges formed by a Miller plateau phase during a switch-off phase of the IGBT device;

measuring a time delay between the obtained pulses indicating the start and end of the Miller plateau phase during the switch-off phase of the IGBT device; and

determining at least one of the junction temperature and the remaining lifetime of the IGBT device based on the measured time delay.

14. The method according to claim 13 , wherein the junction temperature of the IGBT device is further determined based on a collector-emitter voltage and an IGBT device current.

15. The method according to claim 13 , wherein at least one of the junction temperature of the IGBT device and an indication of the remaining lifetime is determined by means of at least one of a look-up table and a mathematical function.

16. The method according to claim 13 , comprising:

selecting the pulses indicating the start and end of the Miller plateau phase during the switch-off phase of the IGBT device from other pulses, wherein the selecting of the pulses comprises:

filtering pulses based on a reference switch voltage as a threshold level, and

generating the respective threshold levels based on the amplitudes of the obtained pulses.

17. The method according to claim 13 , comprising:

selecting the pulses indicating the start and end of the Miller plateau phase during the switch-off phase of the IGBT device from other pulses, wherein the selecting of the pulses comprises:

comparing voltage levels of pulses with a respective reference switch voltage as a threshold level to obtain binary pulse signals; and

generating the respective threshold levels based on the amplitudes of the obtained pulses.

18. The method according to claim 17 , comprising:

applying a hysteresis when comparing the voltage levels of pulses with the respective reference switch voltage as a threshold level to obtain the binary pulse signals.