Method and apparatus for operating a power semiconductor module and gate driver chip

Abstract

Method for operating a power semiconductor module (2), wherein the power semiconductor module (2) comprises at least one parallel connection of at least two power transistors (T1, T2;T3, T4) with isolated gate terminals (G1 - G4), wherein the gate terminals (G1 - G4) of the power transistors (T1 - T4) are individually accessible and can be individually controlled by at least one gate driver IC (3, 4), wherein a characteristic curve (K) of the threshold voltage versus the temperature (T) is stored in a memory (5), wherein in an initialization step the threshold voltage of each power transistor (T1 - T4) is measured at a currently available temperature (T) and an adapted characteristic curve (K') is stored for each power transistor (T1 - T4) based on the measured threshold voltage, wherein in operation the threshold voltages of the power transistors (T1 - T4) are detected and a temperature (T) of each individual power transistor (T1 - T4) is determined from this, wherein in case of a deviation of 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.;

Description

[0001] The invention relates to a method and a device for operating a power semiconductor module and a gate driver component.

[0002] SiC MOSFETs, in particular, are often connected in parallel in power modules for automotive applications such as pulse-controlled inverters. This is due to the power requirements of the electric motors, which cannot be met by a single SiC MOSFET. The individual chips have relatively large control ranges (e.g., ± 30% for Rdson and gate threshold voltages). The thermal paths can also vary, so that worst-case scenarios typically lead to oversizing. One solution is to sort the chips into so-called "bins," where similar chips are selected. However, this is cumbersome and only possible to a limited extent. Similar problems can also arise with iGBTs.

[0003] From US 2011 / 0 018 593 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 is controlled into a range in which a small current still flows.

[0004] DE 199 20 505 A1 and US 2022 / 0 231 595 A1 each disclose a method for operating a power semiconductor module, wherein the power semiconductor module has at least one parallel circuit of at least two power transistors with insulated gate terminals, wherein the gate terminals of the power transistors are individually exposed and can be individually controlled by at least one gate driver component. Temperature sensors determine the respective temperature of the power transistors, and if there is a temperature deviation between at least two power transistors, the control of at least one of the power transistors is changed to counteract the deviation.

[0005] US 2017 / 0 003 337 A1 discloses temperature monitoring of an IGBT based on temperature-sensitive parameters, with the threshold voltage being used as a parameter, among others.

[0006] The technical article "Strauss, B.; Lindemann, A.: Measuring the junction temperature of an IGBT using its threshold voltage as a temperature-sensitive electrical parameter (TSEP). In: 13th International Multi-Conference on Systems, Signals & Devices (SSD), 2016, pp. 459-467" describes a method for detecting the temperature of an IGBT in a module. The threshold voltage is used as a temperature-sensitive parameter, and the characteristic curve of the threshold voltage versus temperature is stored in an initialization step. If a maximum temperature is exceeded, the IGBT is no longer activated during operation.

[0007] The invention is based on the technical problem of providing a method for operating a power semiconductor module in which problems due to tolerances of the individual transistors are reduced. A further technical problem is the creation of a suitable device and a suitable gate driver component.

[0008] The solution to the technical problem results from a method having the features of claim 1, a device having the features of claim 9 and a gate driver module having the features of claim 10. Further advantageous embodiments of the invention result from the subclaims.

[0009] A method is proposed 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 terminals, wherein the gate terminals of the power transistors are individually brought out and can be individually controlled by a gate driver component. 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 average power transistor in the production series. In an initialization step, the threshold voltage of each power transistor is measured at a currently prevailing temperature, wherein the temperature is measured, for example, by means of a temperature sensor. In this case, the drain current orCollector current is kept as low as possible to prevent a temperature increase during the measurement. An adjusted characteristic curve is then saved for each power transistor based on the measured threshold voltage. The adjustment is preferably performed 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 from this, the temperature of each individual power transistor is determined using its adjusted characteristic curve. If there is a temperature deviation between at least two power transistors, the control of at least one of the power transistors is changed to counteract the deviation. This symmetrical behavior so that the power transistors are loaded more evenly. The deviation can be absolute (e.g.It can be relative (e.g., 2-10°C) or relative (e.g., 2-5% warmer or cooler). In a power MOSFET, the threshold voltage is also called the gate threshold voltage.

[0010] In one embodiment, a warmer power transistor is switched faster and / or a cooler power transistor is switched slower. In current-controlled gate driver components, this is achieved by adjusting the current level, and in voltage-controlled gate driver components, this is achieved by adjusting the gate resistance or the gate voltage.

[0011] In a further embodiment, the determined temperatures of the power transistor are verified for plausibility using the threshold voltages by at least one further temperature measurement and / or temperature determination. The measurement can be performed, for example, using the temperature sensor from the initialization phase and / or another temperature sensor.

[0012] In a further embodiment, the contact resistance Rdson or R ceon The temperature of the parallel circuit is determined, and a temperature for the power transistors is calculated from this. This averaged temperature is often sufficient for plausibility purposes to detect measurement errors in the threshold voltage or gate threshold voltage.

[0013] In another embodiment, the drain current or collector current is set constant by a current source during the initialization step, which improves the accuracy of the measurement. The current source is preferably part of the gate driver component.

[0014] In another embodiment, if a detected threshold voltage exceeds a threshold value, an error signal is generated for the associated power transistor, allowing the transistor to be replaced, for example, or the control system to be 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, for example, 3 V).

[0015] In a further embodiment, the power semiconductor module is part of a traction system of a motor vehicle, with the initialization step being performed when the motor vehicle is started. This can be performed at every start. It can also be provided that a certain time must elapse between starts so that all thermal equalization processes are completed.

[0016] 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 through, so that a short circuit of the operating voltage is avoided.

[0017] The device for operating at least one power semiconductor module comprises a power semiconductor module with a parallel circuit of at least two power transistors with insulated gate terminals, wherein the gate terminals of the power transistors are individually led out and can be individually controlled by at least one gate driver module, wherein the device further comprises at least one memory and at least one temperature sensor, wherein a characteristic curve of the threshold voltage versus temperature is stored in the memory, wherein the device is further designed such that in an initialization step, the threshold voltage of each power transistor is measured at a currently prevailing temperature and an adapted characteristic curve is stored for each power transistor based on the measured threshold voltage,During operation, the threshold voltage is detected, and a temperature of each individual power transistor is determined therefrom. If there is a temperature deviation between at least two power transistors, the control of at least one of the power transistors is changed to counteract the deviation. Regarding further embodiments, reference is made to the preceding procedural embodiments, to which reference is made in full.

[0018] The gate driver module for controlling at least two parallel-connected power transistors with individual 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 such that, in an initialization step, the threshold voltage of each power transistor is measured at a currently prevailing temperature, and for each power transistor, an adapted characteristic curve is stored based on the measured threshold voltage. During operation, the threshold voltages of the power transistors are recorded, and a temperature of each individual power transistor is determined from this based on the adapted characteristic curve. If there is a temperature deviation between at least two power transistors, the control of at least one of the power transistors is changed to counteract the deviation.

[0019] With regard to further details, reference is made in full to the preceding statements.

[0020] The power transistors are preferably SiC MOSFETs. However, the power transistors can also be IGBTs or MOSFETs using other technologies. The power semiconductor module is preferably an inverter for the traction network of an electric or hybrid vehicle.

[0021] The invention is explained in more detail below using preferred embodiments. The figures show: Fig. 1 a schematic representation of a device for operating a power semiconductor module and Fig. 2 a schematic characteristic curve of the gate threshold voltage versus temperature.

[0022] In the Fig. 1 schematically shows a device 1 for operating a power semiconductor module 2. The power semiconductor module 2 is designed as a half-bridge circuit, with two power transistors T1, T2 connected in parallel as high-side switches and two power transistors T3, T4 connected as low-side switches. The power transistors T1 - T4 are designed as MOSFETs. The number of transistors connected in parallel can also be larger, for example, between 4 and 8. The gate terminals G1 - G4 are individually led out. The gate terminals G1, G2 of the high-side switches are connected to a gate driver module 3, and the gate terminals G3 and G4 of the low-side switches are connected to a gate driver module 4, with the gate driver modules 3, 4 being designed to control the gate terminals G1 - G4 independently of one another.The power semiconductor module 2 further comprises at least one voltage measuring device (not shown) and at least one current measuring device (not shown) for measuring the respective drain-source voltage U. DS and the drain current I D through the parallel circuit. These measured values ​​are each fed to the associated 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 further comprise 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 comprise switchable current sources 7 to maintain a constant drain current I Din an initialization step.

[0023] In the memory 5, a characteristic curve of the gate threshold voltage U GS stored above the temperature T (see Fig. 2). This characteristic curve is preferably specified by the manufacturer and can be found in a data sheet. This characteristic curve is subject to significant tolerances. It should be noted that, in this context, the term "characteristic curve" also refers to 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 are also fed to the gate driver module 3, 4.

[0024] Due to manufacturing tolerances, the power transistors T1 - T4 differ in their parameters (e.g., gate threshold voltage). Without countermeasures, this would lead to varying levels of stress on the power transistors T1 - T4 during operation, so that power transistors T1 - T4 subjected to higher loads would be more likely to fail.

[0025] To avoid this problem, an initialization step is performed before actual commissioning. This assumes that the power semiconductor module 2 is thermally stable before startup and that the temperature T measured by temperature sensor 8 matches the temperature Tj of the power transistors T1 - T4. The gate driver modules 3 and 4 then successively determine the gate threshold voltage U GS each power transistor T1 - T4. Based on the measured values ​​for the gate threshold voltage U GSAt the current temperature T, the characteristic curve for each power transistor T1 - T4 is adjusted by shifting it so that the characteristic curve passes through the measurement point. The adjusted characteristics for each power transistor T1 - T4 are then saved.

[0026] For the measurement, the drain current I D kept constant at a low level by the current sources 7 (e.g. 20 mA), so that there is no significant temperature increase or current change during the measurement.

[0027] During operation of the power semiconductor module 2, the gate threshold voltages U GSThe temperature of the power transistors T1 - T4 is determined, and from this, the respective temperature T of the individual power transistors T1 - T4 is determined using the adjusted characteristic curves. If the temperatures T of parallel-connected transistors differ 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 cooler transistor can be switched slower, thus distributing the current more evenly during switching.

[0028] Since the contact 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 contact resistance Rdson, even if the temperature goes across the parallel circuit during operation due to the contact resistance Rdson and is thus averaged.

[0029] Furthermore, at a certain value for the gate threshold voltage U GS an error can be concluded and a warning signal can be generated.

[0030] A preferred application is the use in an inverter of a traction network of an electric or hybrid vehicle, in which case three half-bridges are used, whereby the initialization step can be carried out in parallel in the three half-bridges.

[0031] In the Fig. 2 is a characteristic curve K of the gate threshold voltage U GSand adjusted characteristic curve K' based on a gate threshold voltage measurement in the initialization step versus temperature T for a power MOSFET. List of reference symbols 1) Device 2) Power semiconductor module 3) Gate driver module 4) Gate driver module 5) Storage 6) Microprocessor 7) Power sources 8) Temperature sensor G1 - G4 gate connections I D Drain current K characteristic curve K' adjusted characteristic curve T Temperature T1 - T4 power transistor U DS Drain-source voltage U GS Gate threshold voltage

Claims

[1] Method for operating a power semiconductor module (2), wherein the power semiconductor module (2) has at least one parallel circuit of at least two power transistors (T1, T2;T3, T4) with insulated gate terminals (G1 - G4), wherein the gate terminals (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), wherein a characteristic curve (K) of the threshold voltage versus the temperature (T) is stored in a memory (5), wherein in an initialization step the threshold voltage of each power transistor (T1 - T4) is measured at a currently existing temperature (T) and an adapted characteristic curve (K') is stored for each power transistor (T1 - T4) on the basis of the measured threshold voltage, wherein during operation the threshold voltages of the power transistors (T1 - T4) are recorded and a temperature (T) of each individual power transistor (T1 - T4) is determined therefrom, wherein in the event of 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.; [2] Method according to claim 1, characterized by that a warmer power transistor (T1 - T4) is switched faster and / or a colder power transistor (T1 - T4) is switched slower. [3] Method according to claim 1 or 2, characterized by 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. [4] Method according to claim 3, characterized by that a contact resistance (Rdson) of the parallel circuit is determined and from this a temperature (T) for the power transistors (T1, T2; T3, T4) is determined. [5] Method according to one of the preceding claims, characterized by that in the initialization step the drain current (I D) or collector current is set constant by a current source (7). [6] Method according to one of the preceding claims, characterized by that when a detected threshold voltage is greater than a threshold value, an error signal is generated for the associated power transistor (T1 - T4). [7] Method according to one of the preceding claims, characterized by that the power semiconductor module (2) is a component of a traction network of a motor vehicle, wherein the initialization step is carried out when the motor vehicle is started. [8] Method according to one of the preceding claims, characterized bythat the power semiconductor module (2) is an inverter of an electric machine, wherein in the event of a detected or imminent 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 through. [9] Device (1) for operating at least one power semiconductor module (2), wherein the device (1) has a power semiconductor module (2) with a parallel circuit of at least two power transistors (T1, T2; T3, T4) with insulated gate terminals (G1 - G4), wherein the gate terminals (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), wherein the device (1) further has at least one memory (5) and at least one temperature sensor (8), wherein a characteristic curve (K) of the threshold voltage over the temperature (T) is stored in the memory (5), wherein the device (1) is further designed such thatthat in an initialization step, the threshold voltage of each power transistor (T1 - T4) is measured at a currently existing temperature (T) and for each power transistor (T1 - T4) an adapted characteristic curve (K') is stored on the basis of the measured threshold voltage, wherein during operation the threshold voltage is recorded and a temperature (T) of each individual power transistor (T1 - T4) is determined therefrom, wherein in the event of 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. [10] Gate driver module (3, 4) for controlling at least two parallel-connected power transistors (T1, T2; T3, T4) with individual gate control, wherein the gate driver module (3, 4) has at least one memory (5), wherein a characteristic curve (K) of the threshold voltage over the temperature (T) is stored in the memory (5), wherein the gate driver module (3, 4) is designed such that in an initialization step the threshold voltage of each power transistor (T1 - T4) is measured at a currently existing temperature (T) and for each power transistor (T1 - T4) an adapted characteristic curve (K') is stored on the basis of the measured threshold voltage, wherein during operation the threshold voltages of the power transistors (T1 - T4) are recorded and a temperature (T) of each individual power transistor (T1 - T4) is determined therefrom, wherein in the event of a deviation of 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.;

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