US-12625014-B2 - Method and electronic device for monitoring the temperature of power electronics, and motor vehicle

US12625014B2US 12625014 B2US12625014 B2US 12625014B2US-12625014-B2

Abstract

A method and an electronic device monitors the temperature of power electronics having at least one power transistor. In the method, during active operation of the power transistor, the drain-source voltage and the drain current of the transistor are measured and are used to calculate an on-state resistance. An instantaneous junction temperature of the power transistor is determined for monitoring the temperature on the basis of a predefined assignment. The predefined assignment is automatically recalibrated for future operation of the power transistor by automatically measuring in each case a pair of values of the instantaneous on-state resistance and an instantaneous temperature of the power electronics in each case at a plurality of different times outside active operation. These temperatures are measured at a location spatially spaced apart from the junction of the power transistor and are assumed to be junction temperatures prevailing at the respective time. The assignment is then updated according to these pairs of values.

Inventors

Said El-Barbari

Assignees

BAYERISCHE MOTOREN WERKE AKTIENGESELLSCHAFT

Dates

Publication Date: 20260512
Application Date: 20210621
Priority Date: 20200622

Claims (11)

1 . 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 power 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 a 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 temporal 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; 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.
2 . The method according to claim 1 , wherein the predefined criterion is an exceeding of a predefined threshold value.
3 . The method according to claim 1 , wherein a temperature for the recalibration operations is measured by a temperature sensor, which is arranged on a substrate of a module comprising the power transistor.
4 . The method according to claim 3 , wherein the temperature sensor is an NTC thermistor.
5 . The method according to claim 1 , wherein the power electronics have a desaturation detection circuit and the drain-source voltage is measured using the desaturation detection circuit.
6 . The method according to claim 1 , wherein the drain-source voltage is measured only after a predefined settling time after a respective operation of switching on the power transistor has elapsed and, in each case, is measured only when a respective switched-on duration, which remains after the predefined settling time and for which the power transistor remains switched on without interruption, corresponds at least to a predefined minimum duration.
7 . The method according to claim 1 , wherein an electrical machine is connected to the power electronics, a current vector is automatically determined for the recalibration and is usable to guide a current through the electrical machine without producing a torque, and the current having the determined current vector is then guided through the power transistor and into the electrical machine in order to measure an on-state resistance during the recalibration.
8 . 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.
9 . The method according to claim 1 , wherein a predefined starting temperature of the power electronics and/or a predefined temperature profile while respectively measuring the pairs of values is automatically set for the recalibration by a thermal preconditioning device.
10 . 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.
11 . A motor vehicle, comprising: at least one electronic device according to claim 10 , wherein the electronic device is part of an electrical drive train.

Description

CROSS REFERENCE TO RELATED APPLICATION This application claims priority under 35 U.S.C. § 119 from German Patent Application No. 10 2020 116 424.6, filed Jun. 22, 2020, the entire disclosure of which is herein expressly incorporated by reference. BACKGROUND AND SUMMARY OF THE INVENTION The present invention relates to a method and an electronic device for monitoring the temperature of power electronics and to a corresponding motor vehicle. When using semiconductor-based electrical and electronic components, the operating temperature is an important factor for efficient and simultaneously safe operation. In the case of high load requirements, high temperatures may arise very quickly and can result in damage to the respective component part. If, in contrast, a reliable and operationally safe temperature range is not used up, a full power or performance of the respective component part accordingly often cannot be used up either. On account of the small structure sizes and the high packing density in modern electronic component parts and the installation space which is valuable in terms of costs, it is not readily possible to precisely and reliably measure the actual temperatures inside the electronic components. An important parameter is the so-called junction temperature inside a semiconductor transistor or transistor chip. This temperature could be at least approximately directly measured by directly arranging a PN diode on the respective transistor chip, for example, the forward voltage of which diode varies linearly with the temperature. However, this uses valuable chip area, for example 15% to 20% of an active area of a chip, and is therefore not practical in many applications. Nowadays, a temperature sensor is therefore often arranged on a substrate or housing of a module comprising a plurality of power transistors in order to monitor the temperature. However, since the temperature inside such a module can vary significantly over the different power transistors, only a type of mean value of the temperatures inside the module can therefore be measured. A temperature measured in this manner is therefore referred to, for example, as a virtual junction temperature (Tjv). In addition, on account of the heat transfer coefficients and the thermal inertia of the material in between, such temperature sensors arranged at a certain distance from the actual junction often cannot be used to detect rapid temperature increases reliably or quickly enough to prevent damage. Against this background, EP 2 270 983 A1, for example, discloses an integrated smart power switch. That document describes a controllable semiconductor device having a controller for controlling a first operating parameter according to predefined data, including a curve for a transient thermal impedance between a junction and a housing for a normal mode and an avalanche mode. If a comparison of the predefined data with a predicted value satisfies a particular condition, a condition for a safe operating range should then be determined on the basis, inter alia, of a reliability characteristic of the semiconductor device. Accordingly, safe and reliable operation of the semiconductor device should then be achieved by accordingly dynamically modifying the first operating parameter. It is also possible to use a method for calibrating installed power devices, in which a housing temperature of the device after pulse loading is observed. This method is based on the ability of a thermal impedance between a housing and a heat sink to handle power. The junction temperature plays a role in another field of application, for example in photovoltaic panels as well. US 2012/0 212 064 A1 describes a method for controlling such a photovoltaic panel in a three-phase power generation system. The junction temperature can be calculated therein on the basis of a model of the panel, for example from a temperature on a rear side of the panel. The junction temperature is used, for example, to evaluate an electrical model of the panel. In this respect, the junction temperature can be measured directly if the panel has a corresponding temperature sensor which is integrated in a photovoltaic cell. However, the problem of the junction temperature being determined only indirectly or in a model-based manner and therefore with a delay and/or in an unreliable manner or a large amount of installation space accordingly being required for a specific temperature sensor is not circumvented here either. Furthermore, U.S. Pat. No. 9,030,054 B2 describes a method for adaptively controlling a gate driver. A set of sensors can be used therein to detect a set of operating parameters of a semiconductor switch. In this case, this set of operating parameter comprises, inter alia, a junction temperature. The method for calibrating power devices, mentioned in connection with EP 2 270 983 A1, can also be used here. However, this method also does not provide for the junction temperature to be determined