DEVICE AND METHOD FOR DETERMINING THE AGING STATE OF AT LEAST A POWER SHELL SWITCH

Description

[0001] The invention relates to a device and a method for determining the aging state of at least one power semiconductor switch.

[0002] Power semiconductor switches are used in a wide variety of applications, for example in traction networks for electric or hybrid vehicles or as inverters in wind turbines. For smooth operation, it is important to identify and replace severely aged power semiconductor switches such as MOSFETs or IGBTs as soon as possible, ideally before they fail.

[0003] It is known that the contact resistance increases with age. It is further known that the contact resistance depends on the temperature and the forward current.

[0004] From CN 112485632 A, a device for determining the aging state of an IGBT is known, wherein the device comprises an evaluation unit and a temperature sensing device. Voltage, current, and temperature are measured. By comparison with stored characteristic curves, the aging state is then determined.

[0005] From EP 3 492 935 B1 a method for determining an aging state of a power semiconductor switch is known, wherein the voltage drop at two different current values ​​at the same temperature is recorded, wherein this is repeated, and an aging state is determined from the measurement results.

[0006] From US 2014 / 0125366 A1, a method for determining the aging state of an IGBT is known, wherein the voltage drop due to a predefined current at a set temperature is determined, wherein the measurement is carried out when the IGBT is not in operation, and the aging state is inferred from the change in the voltage drops.

[0007] A method for predicting a fault in a power semiconductor switch is known from US patent 2019 / 0033362 A1.

[0008] From DE 10 2019 205 043 A1, a transformer device is known comprising at least one power component and a detection device configured to detect voltage measurements of the power component and current measurements of the secondary winding and / or the primary winding of the transformer. An evaluation unit is provided that determines at least one first wear-indicating parameter from a voltage and a current measurement. The detection device is further configured to detect temperature measurements from a temperature sensor mounted on the power component and transmit them to the evaluation unit. The evaluation unit then determines a second wear-indicating parameter from the temperature profile.

[0009] From DE 10 2015 223 470 A1, a semiconductor device is known comprising a substrate and a first temperature measuring element, wherein the first temperature measuring element is arranged near a location of high power dissipation of the semiconductor device, and wherein a second temperature measuring element is arranged spatially separated from the first temperature measuring element on the substrate. A current is then calculated from the two temperature measurements.

[0010] From EP 2 388 563 A2, a method for determining the temperature of a power semiconductor is known, in which a first control contact is connected to a first pole of a series resistor integrated in the power semiconductor, wherein a second pole of the series resistor, leading to the power semiconductor, is connected to a second control contact. The control contacts are connected to terminals, whereby the value of the series resistor is determined by measurement and a temperature value is derived from this using a characteristic curve.

[0011] From DE 10 2020 214 678 A1, another method for estimating a junction temperature of a power semiconductor device is known.

[0012] The invention addresses the technical problem of creating a device for determining the aging state of at least one power semiconductor switch, thereby improving accuracy. A further problem is providing a suitable method.

[0013] The solution to the technical problem is achieved by a device having the features of claim 1 and a method having the features of claim 7. Further advantageous embodiments of the invention are set forth in the dependent claims.

[0014] For this purpose, the device for determining the aging state of at least one power semiconductor switch comprises at least one evaluation unit and a device for detecting or determining the temperature of the power semiconductor switch. The evaluation unit is configured to access characteristic curves of a contact resistance over the aging state. Here, "characteristic curve" is generally understood as a mapping rule and also includes lookup tables. The characteristic curves are parameterized with various temperatures of the power semiconductor switch. The evaluation unit is configured to detect a voltage value across the power semiconductor switch at a predetermined current value through the power semiconductor switch in a closed state and to determine a contact resistance from this.The evaluation unit then assigns an aging state to the power semiconductor switch using the characteristic curves and taking into account the detected or determined temperature. The device includes at least one additional device for detecting or determining the temperature of the power semiconductor switch. The evaluation unit is designed to validate and / or adjust the temperature values ​​of the power semiconductor switch detected or determined by the first device using the temperature values ​​detected or determined by the second device. This improves the aging determination. This approach is based on the understanding that temperature has a significant influence on aging determination, but is difficult to determine precisely, and individual temperature measurements can be distorted by various factors.The ability to validate these readings makes it easier to detect errors. Various combinations of the two devices for sensing or determining the temperature are possible. In particular, more than two devices can be used. For example, one device could be a temperature sensor mounted directly on a semiconductor substrate or directly on the clip.

[0015] In one embodiment, the evaluation unit is designed to assign an estimated end of service life to the aging state of the power semiconductor switch.

[0016] In another embodiment, the evaluation unit is designed to generate a warning signal when the aging condition exceeds a threshold or when the estimated end of service life is less than a threshold, so that a replacement is carried out in a timely manner.

[0017] In a further embodiment, the power semiconductor switch is associated with at least one cooling circuit on which at least one temperature sensor is arranged, wherein the evaluation unit is designed to determine the temperature of the power semiconductor switch from the values ​​of the temperature sensor, taking into account a volume flow rate of the coolant. Depending on the embodiment, the temperature sensor can be the device or a further device for detecting or determining the temperature of the power semiconductor switch.

[0018] According to the invention, the power semiconductor switch is designed as a MOSFET, and the device is configured to determine a gate threshold voltage immediately before and / or after the power semiconductor switch is turned on, whereby a temperature of the power semiconductor switch is assigned to the gate threshold voltage by means of a characteristic curve. This also constitutes a device for determining the temperature, whereby the device can be the first device or at least one further device.

[0019] In another embodiment, several MOSFETs are connected in parallel, and the device is configured to detect the gate threshold voltages of the individual MOSFETs. This makes it possible to infer different temperatures of the MOSFETs, which in turn can indicate different states of aging, especially if other causes for different local temperatures can be ruled out. The gate threshold voltages are preferably determined by one or more gate driver ICs.

[0020] In another embodiment, the MOSFETs are designed as SiC MOSFETs, which, due to their currently still small area, often have to be connected in parallel, since the individual MOSFET does not have sufficient current string capability.

[0021] The method for determining the aging state of at least one power semiconductor switch is performed using an evaluation unit and a device for detecting or determining the temperature of the power semiconductor switch. A voltage value across the power semiconductor switch is detected at a predetermined current value in a closed state, and a contact resistance is calculated from this. Using characteristic curves, an aging state of the power semiconductor switch is assigned to the contact resistance, taking into account the temperature detected or determined by the device. Furthermore, another temperature is detected or determined by a separate device for detecting or determining the temperature of the power semiconductor switch. This additional temperature is used to verify and / or adjust the temperature detected or determined by the device.Regarding further procedural details, full reference is made to the preceding statements.

[0022] The invention is explained in more detail below with reference to preferred embodiments. The figures show: Fig. 1 a schematic representation of a device for determining the aging state of at least one power semiconductor switch, Fig. 2 a schematic representation of a through-resistance across the SOH, Fig. 3 a schematic representation of a gate threshold voltage versus temperature, and Fig. 4 a schematic representation of a parallel connection of MOSFETs.

[0023] In the Fig. 1 A schematic representation of a device 1 for determining the aging state of at least one power semiconductor switch 2, represented here as an IGBT 3, is shown. The device 1 includes an evaluation unit 4 and a device 5 for detecting or determining the temperature T of the power semiconductor switch 2. Furthermore, the device 1 comprises a current measuring device 6 for detecting the current I through the power semiconductor switch 2. The position of the current measuring device 6 is shown here for illustrative purposes only. In a pulse inverter, the current in the center taps to the electric motor is preferably measured, since the inductances of the electric motor dampen the rapid current changes resulting from the pulsed operation of the power semiconductor switch 2. The current I through the power semiconductor switch is then determined from this measured current.Furthermore, the device 1 includes a voltage measuring device 7 for detecting the voltage U across the power semiconductor switch 2. A cooling circuit 8 is also shown, wherein a pump 9 can circulate coolant past the power semiconductor switch 2, although the cooling circuit is not shown in its entirety. The pump 9 is controlled by a control unit 10. A further device 11 for detecting or determining the temperature of the power semiconductor switch 2, for example in the form of a temperature sensor, is arranged on an outer wall of the cooling circuit 8. The device 5 is preferably a temperature sensor that is arranged directly on a housing 12 of the power semiconductor switch 2. Alternatively, the device 5 is designed as a temperature sensor that is arranged on the substrate of the power semiconductor switch 2 or on the clip.Evaluation unit 4 receives the temperature values ​​from device 5 and the other device 11, as well as the current value I and the voltage value U. Furthermore, evaluation unit 4 receives the coolant flow rate V from control unit 10. To determine the aging state of the power semiconductor switch 2, the IGBT 3 is switched on during operation and a predefined current I is set. The set current value I and the resulting voltage U are then transmitted to the evaluation unit, which calculates a contact resistance Ron. The temperature value T transmitted by device 5 is then validated and / or adjusted using the temperature value from device 11. If, for example, both devices 5 and 11 exhibit high accuracy, an average value can be calculated.If, however, the accuracy of device 5 is typically higher, the temperature value of device 11 is only used to validate the temperature value of device 5. This allows, for example, the detection of a defect in device 5. Furthermore, there are conceivable cases where neighboring heat sources could distort the temperature measurement. Using the validated temperature of device 5, a state-of-health (SOH) value is then determined in a characteristic curve, with the SOH value decreasing as the device ages (see also...). Fig. 2 ), where the characteristic curves are parameterized with temperature. From the SOH value or the state of aging, the remaining service life or the estimated end of service life can then be deduced.

[0024] In the Fig. 3 The diagram schematically shows the relationship between the gate threshold voltage Uth of a MOSFET and the temperature T, where the gate threshold voltage Uth decreases with increasing temperature T. This can now be used to design a device 5 or another device 11. Knowing the gate threshold voltage allows us to determine the temperature T.

[0025] This is particularly advantageous in a circuit configuration such as in Fig. 4 The diagram shows four MOSFETs MF1-MF4 connected in parallel, where the MOSFETs MF1-MF4 are, for example, SiC MOSFETs. Often, only the total current I is measured, and only one temperature sensor is used for all MOSFETs MF1-MF4 due to space constraints. Therefore, the determined on-resistance Ron is an average, as it is assumed that ideally all MOSFETs MF1-MF4 are identical and age at the same rate, which is not necessarily the case in reality. If, for example, a gate driver IC 13 controls the individual gates G1-G4 individually, it can determine the respective gate threshold voltage Uth of the MOSFETs MF1-MF4 and thus assign an individual temperature T to each MOSFET MF1-MF4 according to the relationship... Fig. 3 assign and determine the aging individually for the MOSFETs MF1-MF4. Reference symbol list

[0026] 1 Device 2 Power semiconductor switch 3 IGBT 4 Evaluation unit 5 Device 6 Current measuring device 7 Voltage measuring device 8 Cooling circuit 9 Pump 10 Control unit 11 Device 12 Housing 13 Gate driver module T Temperature I Current U Voltage V Volume flow MF1-MF4 MOSFET U th Gate threshold voltage G1-G4 Gates

Claims

1. Device (1) for ascertaining an aging condition of at least one power semiconductor switch (2), the device (1) comprising at least one evaluation unit (4) and an apparatus (5) for detecting or determining a temperature (T) of the power semiconductor switch (2), the evaluation unit (4) being designed to access characteristic curves of a contact resistance (Ron) via the aging condition, the characteristic curves being parameterized with different temperatures (T) of the power semiconductor switch (2), the evaluation unit (4) being further designed to detect a voltage value (U) across the power semiconductor switch (2) at a predetermined current value (I) via the power semiconductor switch (2) in a through-connected state and to calculate a contact resistance (Ron) from said voltage value, the evaluation unit (4) then assigning an aging condition to the power semiconductor switch (2) by means of a characteristic curve, taking into account the temperature (T) of the power semiconductor switch (2) detected or determined by the apparatus (5), characterized in that the device (1) comprises at least one further apparatus (11) for detecting or determining the temperature (T) of the power semiconductor (2), the evaluation unit (4) being designed to check the plausibility and / or adapt the temperature values of the power semiconductor switch (2) detected or determined by means of the apparatus (5), by means of the temperature values of the power semiconductor switch (2) detected or determined by the at least one further apparatus (11), the power semiconductor switch (2) being designed as a MOSFET (MF1-MF4), the device (1) being designed to determine a gate threshold voltage (Uth) immediately before and / or after the power semiconductor switch (2) is through-connected, the gate threshold voltage (Uth) being assigned a temperature (T) of the power semiconductor switch (2) by means of a characteristic curve.

2. Device according to claim 1, characterized in that the evaluation unit (4) is designed to assign an estimated end of service life to the aging condition of the power semiconductor switch.

3. Device according to claim 1 or claim 2, characterized in that the evaluation unit (4) is designed to generate a warning signal in the event of an aging condition greater than a threshold value or in the event of an estimated end of service life less than a threshold value.

4. Device according to any of the preceding claims, characterized in that the power semiconductor switch (2) is associated with least one cooling circuit (8),with which at least one temperature sensor is associated, the evaluation unit (4) being designed to determine a temperature of the power semiconductor switch (2) from the values of the temperature sensor, taking into account a volume flow (V) of the coolant.

5. Device according to any of the preceding claims, characterized in that a plurality of MOSFETs (MF1-MF4) are connected in parallel, the device (1) being designed to detect the gate threshold voltages (Uth) of the individual MOSFETs (MF1-MF4).

6. Device according to any of the preceding claims, characterized in that the MOSFETs (MF1-MF4) are designed as SiC MOSFETs.

7. Method for ascertaining an aging condition of at least one power semiconductor switch (2), by means of a device (1) comprising at least one evaluation unit (4) and an apparatus (5) for detecting or determining a temperature (T) of the power semiconductor switch (2), a voltage value (U) across the power semiconductor switch (2) being detected at a predetermined current value (I) via the power semiconductor switch (2) in a through-connected state, and a contact resistance (Ron) being calculated from said voltage value, the calculated contact resistance (Ron) being assigned an aging condition of the power semiconductor switch (2) by means of characteristic curves, taking into account the temperature (T) detected or determined by the apparatus, characterized in that by means of at least one further apparatus (11) for detecting or determining the temperature (T) of the power semiconductor switch (2), a further temperature (T) is detected or determined, which is used for the plausibility check and / or adaptation of the temperature detected or determined by the apparatus (5), the power semiconductor switch (2) being designed as a MOSFET (MF1-MF4), the device (1) being designed to determine a gate threshold voltage (Uth) immediately before and / or after the power semiconductor switch (2) is through-connected, the gate threshold voltage (Uth) being assigned a temperature (T) of the power semiconductor switch (2) by means of a characteristic curve.