Indirect measurement of junction temperature for condition monitoring of power semiconductor devices during operation

Inhalt:
In a power converter, the monitoring of junction temperature Tvj is imperative for overtemperature or overload protection. Further, comparing measured junction temperature during operation with the temperature value calculated by a suitable model allows condition monitoring, i. e. to detect wearout or a deteriorated thermal interface. Since junction temperature within a device can’t be directly measured, it is determined indirectly instead. This paper presents a relatively simple circuit to be added to an IGBT driver which permits to monitor junction temperature of the chip during converter operation as has been demonstrated.