Method and electronic device for monitoring the temperature of power electronics, and motor vehicle

A method for monitoring temperature of power electronics comprising at least one power transistor, the method comprising:

• during active operation of the power transistor, measuring a drain-source voltage and a drain current for the transistor and using the drain-source voltage and the drain current to calculate an on-state resistance;
• determining an instantaneous junction temperature of the power transistor that is assigned to the calculated on-state resistance on the basis of a predefined assignment as a key figure for monitoring the temperature;
• automatically recalibrating the predefined assignment for future operation of the power transistor by automatically measuring in each case a pair of values of an instantaneous on-state resistance of the power transistor and an instantaneous temperature of the power electronics in each case at a plurality of different times in each case outside active operation of the power transistor;
• capturing a temporal change in an assignment over a plurality of recalibration operations and automatically outputting a warning indicating a need for maintenance on the power electronics in a case in which the captured temporal change satisfies a predefined criterion for a specific pattern of change in the assignment, wherein
• the temperatures are measured at a location spatially spaced apart from a junction of the power transistor and are assumed to be junction temperatures prevailing at a respective time, and the assignment is updated according to the pairs of values, and all the junction temperatures are measured at a same time after a homogenous temperature distribution has been reached;
• and
• the junction temperature is repeatedly determined several times during active operation of the power transistor, and a power reduction of the power transistor is automatically controlled on the basis thereof according to a predefined rule;
• determining a cause of the temporal change in the assignment based on the specific pattern;
• determining whether the instantaneous junction temperature reaches or exceeds a first threshold value and automatically reducing a current or a power of the power transistor based on such a determination;
• and
• determining whether the instantaneous junction temperature has fallen below a second threshold value that is lower than the first threshold value and automatically increasing the current or the power of the power transistor based on such a determination.

An electronic device, comprising:

• at least one power electronic component with at least one power transistor;
• a measurement circuit for measuring a drain-source voltage and a drain current of the power transistor during active operation of the latter and for measuring an on-state resistance of the power transistor and a temperature of the power electronics at a location spaced apart from a junction of the power transistor;
• and
• a monitoring device for monitoring the temperature of an electronic device on the basis of a junction temperature of the power transistor,
• wherein the monitoring device is configured to automatically:
• during active operation of the power transistor, measure a drain-source voltage and a drain current for the transistor and use the drain-source voltage and the drain current to calculate an on-state resistance;
• determine an instantaneous junction temperature of the power transistor that is assigned to a calculated on-state resistance on the basis of a predefined assignment as a key figure for monitoring the temperature;
• automatically recalibrate the predefined assignment for future operation of the power transistor by automatically measuring in each case a pair of values of an instantaneous on- state resistance of the power transistor and an instantaneous temperature of the power electronics in each case at a plurality of different times in each case outside active operation of the power transistor;
• and
• capture a temporal change in an assignment over a plurality of recalibration operations and automatically output a warning indicating a need for maintenance on the power electronics in a case in which the captured temporal change satisfies a predefined criterion for a specific pattern of change in the assignment, wherein
• the temperatures are measured at the location spatially spaced apart from the junction of the power transistor and are assumed to be junction temperatures prevailing at a respective time, and the assignment is updated according to the pairs of values, and all the junction temperatures are measured at a same time after a homogenous temperature distribution has been reached;
• determine a cause of the temporal change in the assignment based on the specific pattern;
• determine whether the instantaneous junction temperature reaches or exceeds a first threshold value and automatically reduce a current or a power of the power transistor based on such a determination;
• and
• determine whether the instantaneous junction temperature has fallen below a second threshold value that is lower than the first threshold value and automatically increase the current or the power of the power transistor based on such a determination.