DE102022209659A1 - Method and device for operating a power semiconductor module and gate driver module - Google Patents

Abstract

The invention relates to a method for operating a power semiconductor module (2), wherein the power semiconductor module (2) has at least one parallel connection of at least two power transistors (T1, T2; T3, T4) with insulated gate connections (G1 - G4 ), wherein the gate connections (G1 - G4) of the power transistors (T1 - T4) are led out individually and can be controlled individually by at least one gate driver module (3, 4), a characteristic curve being stored in a memory (5). (K) the threshold voltage is stored above the temperature (T), the threshold voltage of each power transistor (T1 - T4) being measured at a current temperature (T) in an initialization step and for each power transistor (T1 - T4) an adapted characteristic curve (K`) is stored based on the measured threshold voltage, the threshold voltages of the power transistors (T1 - T4) being recorded during operation and a temperature (T) of each individual power transistor (T1 - T4) being determined from this, where if there is a deviation in temperature (T) between at least two power transistors (T1, T2; T3, T4) the control of at least one of the power transistors (T1, T2; T3, T4) is changed in order to counteract the deviation, a device (1) and a gate driver module (3, 4)

Description

The invention relates to a method and a device for operating a power semiconductor module and a gate driver module.

SiC MOSFETs in particular are often connected in parallel in power modules for vehicle applications such as pulse inverters. This is due to the power requirements of the electrical machines, which cannot be supported by a single SiC MOSFET. The individual chips have relatively large controls (e.g. ± 30% for Rdson and gate threshold voltages). The thermal paths can also be different, so oversizing typically occurs due to worst-case scenarios. One solution is to select the chips into so-called “bins”, where similar chips are selected, but this is cumbersome and is only possible to a limited extent. Similar problems can also arise with iGBTs.

From the US 2011/0018593 A1 a gate driver component for a power MOSFET in a DC/DC converter is known, which controls the MOSFET in such a way that it is not completely blocked, but rather is controlled in a range so that a small current still flows.

The invention is based on the technical problem of providing a method for operating a power semiconductor module in which the problems due to tolerances of the individual transistors are reduced. Another technical problem is the creation of a suitable device and a suitable gate driver component.

The solution to the technical problem results from a method with the features of claim 1, a device with the features of claim 9 and a gate driver module with the features of claim 10. Further advantageous embodiments of the invention result from the subclaims.

What is proposed is a method for operating a power semiconductor module, wherein the power semiconductor module has at least one parallel connection of at least two power transistors with insulated gate connections, the gate connections of the power transistors being led out individually and individually through a gate connection. Driver module can be controlled. A characteristic curve of the threshold voltage versus temperature is stored in a memory. This characteristic curve is typically supplied by the manufacturer of the power transistor as a data sheet and represents the relationship for an averaged power transistor of the production series. In an initialization step, the threshold voltage of each power transistor is measured at a current temperature, the temperature being measured, for example, by means of a Temperature sensor is measured. The drain current or collector current is kept as low as possible in order to prevent an increase in temperature during the measurement. An adapted characteristic curve based on the measured threshold voltage is then saved for each power transistor. The adjustment is preferably carried out by shifting the manufacturer's characteristic curve so that it passes through the measured point of the measured threshold voltage at the current temperature. During operation, the threshold voltages of the power transistor are recorded and a temperature of each individual power transistor is determined using its adapted characteristic curve, whereby if there is a deviation in the temperature between at least two power transistors, the control of at least one of the power transistors is changed in order to to counteract deviation. This symmetrizes the behavior so that the power transistors are loaded more evenly. The deviation can be absolute (e.g. 2 - 10° C) or relative (e.g. 2 - 5% warmer or colder). For a power MOSFET, the threshold voltage is also known as the gate threshold voltage.

In one embodiment, a warmer power transistor is switched faster and/or a colder power transistor is switched slower. In the case of current-controlled gate driver components, this is done by adjusting the current level and in the case of voltage-controlled gate driver components, this is done by adjusting the gate resistance or the gate voltage.

In a further embodiment, the determined temperatures of the power transistor are checked for plausibility using the threshold voltages using at least one further temperature measurement and/or determination of the temperature. The measurement can be carried out, for example, using the temperature sensor from the initialization phase and/or another temperature sensor.

In a further embodiment, the volume resistance Rdson or R _ceon of the parallel connection is determined and a temperature for the power transistors is determined from this.

This averaged temperature is often sufficient for plausibility checks in order to detect measurement errors in the threshold voltage or gate threshold voltage.

In a further embodiment, in the initialization step, the drain current or collector current is set constant by a current source, which improves the accuracy of the measurement. The current source is preferably part of the gate driver module.

In a further embodiment, if a detected threshold voltage is greater than a threshold value, an error signal is generated for the associated power transistor, so that it can be replaced, for example, or the control is adjusted, since an increasing threshold voltage indicates an imminent failure. The deviation can again be absolute or relative (e.g. + 20% of the original threshold voltage or e.g. 3 V).

In a further embodiment, the power semiconductor module is part of a traction network of a motor vehicle, with the initialization step being carried out when the motor vehicle is started. Provision can be made for this to occur at every start. It can also be provided that a certain time must have elapsed between starts so that all thermal compensation processes are completed.

In a further embodiment, the power semiconductor module is an inverter of an electric machine, wherein in the event of a detected short circuit of a power transistor or an expected short circuit of a power transistor in an active short circuit of the electric machine, the parallel power transistors of the short-circuited power transistor are permanently switched on so that a short circuit in the operating voltage is avoided.

The device for operating at least one power semiconductor module has a power semiconductor module with a parallel connection of at least two power transistors with insulated gate connections, the gate connections of the power transistors being led out individually and individually through at least one gate driver module can be controlled, the device further having at least one memory and at least one temperature sensor, a characteristic curve of the threshold voltage versus the temperature being stored in the memory, the device being further designed such that in an initialization step, the threshold voltage of each power transistor at a current temperature is measured and an adapted characteristic curve is stored for each power transistor based on the measured threshold voltage, the threshold voltage being recorded during operation and a temperature of each individual power transistor being determined from this, with a deviation in the temperature between at least two power -Transistors, the control of at least one of the power transistors is changed in order to counteract the deviation. With regard to further refinements, reference is made to the previous procedural refinements, to which reference is made in full.

The gate driver module for controlling at least two power transistors connected in parallel with single gate control has at least one memory in which a characteristic curve of the threshold voltage versus temperature is stored. The gate driver module is designed in such a way that in an initialization step the threshold voltage of each power transistor is measured at a current temperature and an adapted characteristic curve based on the measured threshold voltage is stored for each power transistor, the threshold voltages of the power transistors being the same during operation are detected and from this a temperature of each individual power transistor is determined based on the adapted characteristic curve, whereby if there is a deviation in the temperature between at least two power transistors, the control of at least one of the power transistors is changed in order to counteract the deviation.

With regard to the further configurations, reference is made in full to the previous statements.

The power transistors are preferably SiC MOSFETs. The power transistors can also be iGBTs or MOSFETs with other technology. The power semiconductor module is preferably an inverter of a traction network of an electric or hybrid vehicle.

• 1 eine schematische Darstellung einer Vorrichtung zum Betreiben eines Leistungshalbleiter-Moduls und
• 2 eine schematische Kennlinie der Gate-Threshold-Spannung über der Temperatur.

The invention is explained in more detail below using preferred exemplary embodiments. The figures show:

• 1 a schematic representation of a device for operating a power semiconductor module and
• 2 a schematic characteristic curve of the gate threshold voltage versus temperature.

In the 1 A device 1 for operating a power semiconductor module 2 is shown schematically. The power semiconductor module 2 is designed as a half-bridge circuit, with two power transistors T1, T2 being connected in parallel as high-side switches and two power transistors T3, T4 as low-side switches. The power transistors T1 - T4 are designed as MOSFETs. The number of parallel connected Transistors can also be larger and, for example, between 4 and 8. The gate connections G1 - G4 are led out individually. The gate connections G1, G2 of the high-side switch are connected to a gate driver module 3 and the gate connections G3 and G4 of the low-side switch are connected to a gate driver module 4, the gate driver modules 3, 4 are designed to control the gate connections G1 - G4 independently of each other. The power semiconductor module 2 further has at least one voltage measuring device, not shown, and at least one current measuring device, not shown, in order to measure the respective drain-source voltage U _DS and the drain current I _D through the parallel connection. These measured values are each fed to the assigned gate driver modules 3, 4. The gate driver modules 3, 4 can be designed as current or voltage-controlled gate driver modules 3, 4. The gate driver modules 3, 4 also have at least one memory 5 and a microprocessor 6, although these can also be designed as separate components. Furthermore, the gate driver modules 3, 4 are designed to detect the gate threshold voltage as the threshold voltage of the individual power transistors T1, T2 or T3, T4. Finally, the gate driver modules 3, 4 have switchable current sources 7 in order to set a constant drain current I _D in an initialization step.

A characteristic curve of the gate threshold voltage U _GS versus the temperature T is stored in the memory 5 (see Fig. 2 ). This characteristic curve is preferably specified by the manufacturer and can be found on a data sheet. This characteristic curve is subject to high tolerances. It should be noted that in this case the term characteristic curve also means a look-up table. Furthermore, at least one temperature sensor 8 is assigned to the power semiconductor module 2, which is arranged, for example, on a cooling circuit of the power semiconductor module 2, the measured values of the temperature T also being supplied to the gate driver module 3, 4.

Due to manufacturing tolerances, the power transistors T1 - T4 are different in terms of their parameters (e.g. gate threshold voltage). During operation, without countermeasures, this would lead to different levels of loading on the power transistors T1 - T4, so that more heavily loaded power transistors T1 - T4 would be more likely to fail.

To avoid this problem, an initialization step is carried out before the actual commissioning. It is assumed that before starting the power semiconductor module 2 is thermally stable and the temperature T measured by the temperature sensor 8 corresponds to the temperature Tj of the power transistors T1 - T4. The gate driver modules 3, 4 now successively determine the gate threshold voltage U _GS of each power transistor T1 - T4. Based on the measured values for the gate threshold voltage U _GS at the current temperature T, the characteristic curve is then adjusted for each power transistor T1 - T4 by a shift so that the characteristic curve passes through the measuring point. The characteristics adapted in this way for each power transistor T1 - T4 are then saved. For the measurement, the drain current I _D is kept constant at a low level by the current sources 7 (e.g. 20 mA), so that there is no significant increase in temperature or change in current during the measurement.

During operation of the power semiconductor module 2, the gate threshold voltages U _GS of the power transistors T1 - T4 are then determined again and the respective temperature T of the individual power transistors T1 - T4 is determined from this using the adapted characteristic curves. If the temperatures T of transistors connected in parallel differ from one another by an absolute or relative value, this indicates an uneven load and the control is adjusted to counteract the deviation. For example, a warmer transistor can be switched faster and/or a colder transistor can be switched slower in order to distribute the current more evenly during the switching moments.

Since the volume resistance Rdson also depends on the temperature T, the determined temperatures T for the power MOSFETs can be checked for plausibility from the determined temperature T using the volume resistance Rdson, even if the temperature goes over the parallel connection during operation due to the volume resistance Rdson and thus is averaged.

Furthermore, at a certain value for the gate threshold voltage U _GS, an error can be concluded and a warning signal can be generated.

A preferred area of application is use in an inverter of a traction network of an electric or hybrid vehicle, in which case three half-bridges are used, and the initialization step can take place in parallel in the three half-bridges.

In the 2 a characteristic curve K of the gate threshold voltage U _GS and an adapted characteristic curve K` based on a gate threshold voltage measurement in the initialization step are shown over the temperature T for a power MOSFET.

Reference symbol list

1

contraption

2

Power semiconductor module

3

Gate driver module

4

Gate driver module

5

Storage

6

microprocessor

7

Power sources

8th

Temperature sensor

G1 - G4

Gate connections

ID

drain current

K

curve

K`

adapted characteristic curve

T

temperature

T1 - T4

Power transistor

UDS

Drain-source voltage

UGS

Gate threshold voltage

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 20110018593 A1 [0003]

Claims (10)

Method for operating a power semiconductor module (2), wherein the power semiconductor module (2) has at least one parallel connection of at least two power transistors (T1, T2; T3, T4) with insulated gate connections (G1 - G4), wherein the gate connections (G1 - G4) of the power transistors (T1 - T4) are brought out individually and can be controlled individually by at least one gate driver module (3, 4), a characteristic curve (K) being stored in a memory (5). Threshold voltage is stored above the temperature (T), the threshold voltage of each power transistor (T1 - T4) being measured at a current temperature (T) in an initialization step and an adapted characteristic curve (T1 - T4) for each power transistor (T1 - T4). K`) is stored based on the measured threshold voltage, the threshold voltages of the power transistors (T1 - T4) being recorded during operation and a temperature (T) of each individual power transistor (T1 - T4) being determined from this, whereby in the event of a deviation the temperature (T) between at least two power transistors (T1, T2; T3, T4) the control of at least one of the power transistors (T1, T2; T3, T4) is changed in order to counteract the deviation. Procedure according to Claim 1 , characterized in that a warmer power transistor (T1 - T4) is switched faster and / or a colder power transistor (T1 - T4) is switched slower. Procedure according to Claim 1 or 2 , characterized in that the determined temperatures (T) are checked for plausibility by means of the threshold voltage by means of at least one further temperature measurement and/or determination of the temperature. Procedure according to Claim 3 , characterized in that a volume resistance (Rdson) of the parallel connection is determined and from this a temperature (T) for the power transistors (T1, T2; T3, T4) is determined. Method according to one of the preceding claims, characterized in that in the initialization step the drain current ( <sub>ID</sub> ) or collector current is set constant by a current source (7). Method according to one of the preceding claims, characterized in that when a detected threshold voltage is greater than a threshold value, an error signal is generated for the associated power transistor (T1 - T4). Method according to one of the preceding claims, characterized in that the power semiconductor module (2) is part of a traction network of a motor vehicle, the initialization step being carried out when the motor vehicle is started. Method according to one of the preceding claims, characterized in that the power semiconductor module (2) is an inverter of an electric machine, wherein in the event of a detected or impending short circuit of a power transistor (T1 - T4) in an active short circuit of the electric machine, the parallel power Transistors (T1 - T4) of the short-circuited power transistor (T1 - T4) are permanently switched on. Device (1) for operating at least one power semiconductor module (2), the device (1) having a power semiconductor module (2) with a parallel connection of at least two power transistors (T1, T2; T3, T4) with insulated gates. Connections (G1 - G4), wherein the gate connections (G1 - G4) of the power transistors (T1 - T4) are led out individually and can be controlled individually by at least one gate driver module (3, 4), the device ( 1) further has at least one memory (5) and at least one temperature sensor (8), a characteristic curve (K) of the threshold voltage versus the temperature (T) being stored in the memory (5), the device (1) being further designed in this way is that in an initialization step, the threshold voltage of each power transistor (T1 - T4) is measured at a current temperature (T) and an adapted characteristic curve (K`) is stored for each power transistor (T1 - T4) based on the measured threshold voltage is, whereby the threshold voltage is detected during operation and a temperature (T) of each individual power transistor (T1 - T4) is determined therefrom, with a deviation in the temperature (T) between at least two power transistors (T1, T2; T3, T4) the control of at least one of the power transistors (T1, T2; T3, T4) is changed in order to counteract the deviation. Gate driver module (3, 4) for controlling at least two parallel-connected power transistors (T1, T2; T3, T4) with single gate control, the gate driver module (3, 4) having at least one memory (5). , wherein a characteristic curve (K) of the threshold voltage over the temperature (T) is stored in the memory (5), the gate driver module (3, 4) being designed such that in an initialization step, the threshold voltage of each power transistor (T1 - T4) is measured at a current temperature (T) and for each power transistor (T1 - T4) an adapted characteristic curve (K`) is stored based on the measured threshold voltage, the threshold voltages of the power transistors (T1 -T4) being recorded during operation and from this a temperature (T) of each individual power transistor (T1 - T4) is determined, wherein if there is a deviation in the temperature (T) between at least two power transistors (T1, T2; T3, T4), the control of at least one of the power transistors (T1, T2; T3, T4) is changed to counteract the deviation.

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