Method for determining temperature of semiconductor switch and inverter circuit

Abstract

The invention relates to a method for determining the temperature of a semiconductor switch having a control connection, a current input connection and a current output connection, the current input connection is connected to the potential connection via the diode, one connection of the capacitor (the other connection of the capacitor being grounded), the resistor component and the current source. The method comprises: determining a DESAT-voltage occurring at the capacitor at a first moment in time and a second moment in time; determining a load current flowing between a current input connection and a current output connection of the semiconductor switch at a first time; determining a drain-source resistance present between the current input connection and the current output connection of the semiconductor switch at the first time from the DESAT voltage and the load current determined at the first time and the second time; and determining the temperature of the semiconductor switch from the drain-source resistance and the load current. The invention also relates to an inverter circuit for controlling an electric machine.

Description

Field of the Invention

[0001] The present invention relates to a method for determining the temperature of a semiconductor switch and an inverter circuit for performing the method. Background Art

[0002] The blocking layer temperature of semiconductor switches such as IGBTs (insulated gate bipolar transistors), MOSFETs (metal oxide semiconductor field effect transistors), or SiC (silicon carbide)-MOSFETs can be determined by means of temperature sensors that are integrated into the housing or fastened externally to the housing. Usually, temperature sensors are integrated in the power module and can be used to estimate the chip temperature inside the power module. The measured temperature can be used for over-temperature protection, for example, by reducing the power (De-Rating).

[0003] When using sensors, additional isolation and signal guidance for the control board are required; if high voltages are switched by means of semiconductor switches, signal isolators are additionally required. Adding current sensors for each semiconductor switch requires additional space, which is not always available, especially in the case of TO (transistor outline) housings connected to the busbar or circuit board.

[0004] Due to reasons of isolation and interference immunity, the transmission of the measured signal from the terminal board to the control system is very complex. The response time of the sensor is also relatively long.

[0005] Based on the R of the MOSFET Dson it is also possible to determine the temperature of the MOSFET, but this requires a complex circuit to measure the voltage across the switch, especially in the case of high-voltage switches. This measurement also depends to a large extent on the drain current. Summary of the Invention

[0006] According to the present invention, a method for determining the temperature of a semiconductor switch and an inverter circuit for performing the method with the features of the independent claims are proposed. The dependent claims and the subject matter described below are advantageous designs.

[0007] The present invention uses a method in which a simple circuit (hereinafter also referred to as a DESAT - circuit) is used to determine the temperature of a semiconductor switch having a control connection terminal, a current input connection terminal, and a current output connection terminal. The current input connection terminal of the semiconductor switch is connected to a potential connection terminal via a diode, a connection end point of a capacitor, a resistive structural element, and a current source. The other connection end point of the capacitor is grounded. The potential connection terminal can be connected to a positive potential or a positive supply voltage. Appropriately, the current input connection terminal of the semiconductor switch is connected to the cathode of the diode, thereby blocking the current from the semiconductor switch into the DESAT - circuit. The temperature can be estimated from the measurement of the voltage appearing at the capacitor at different times.

[0008] This is particularly advantageous because the known desaturation (DESAT) protection in semiconductor switches can be used for the described circuit configuration with a minimum of additional components, thereby significantly reducing complexity and cost. A commercially standard gate driver - IC (integrated circuit, hereinafter simply referred to as a gate driver) can have a DESAT - connection terminal, and the drain connection terminal of the semiconductor switch is connected to the DESAT - connection terminal as described above via the DESAT - circuit. Thus, the gate driver can monitor the over - current or short - circuit of the semiconductor switch and cut it off in case of a fault. Within the scope of the present invention, the temperature is now also estimated by a special evaluation of the voltage in the DESAT - circuit.

[0009] Specifically, the DESAT - voltage appearing at the capacitor at a first time and a second time is determined, and the load current flowing between the current input connection terminal and the current output connection terminal of the semiconductor switch at the first time is determined. Here, the load current refers to the current flowing through a load (such as a phase winding of a motor) and the semiconductor switch and being switched by the semiconductor switch. In addition, the drain - source resistance existing between the current input connection terminal and the current output connection terminal of the semiconductor switch at the first time is determined from the DESAT - voltage and the load current determined at the first time and the second time, and the temperature of the semiconductor switch is determined from the drain - source resistance and the load current. The load current can be conveniently measured.

[0010] The present invention overcomes the disadvantages of the prior art and in particular brings a series of advantages. Neither temperature measurement nor R DSon is required to measure the temperature of the semiconductor switch, but rather the temperature can be very simply derived from the DESAT - voltage. No temperature sensor is required at or near the switch. The available short - circuit protection (DESAT) uses a minimum of additional components, thereby significantly reducing the cost. The measurement response time is short.

[0011] In the case of correspondingly equipped gate drivers, the data interface can be advantageously used to transfer measurement data to the signal processing electronics (controller), so that then no additional signal transmission is required. Thus, isolation of the measured signal has also been achieved through the isolation of the gate driver.

[0012] The proposed concept can be used for on-line monitoring and on-line fault identification of the temperature of semiconductor switches.

[0013] Since no additional temperature sensors have to be added for each switch, no additional space requirements are created. This is particularly advantageous in the case of a TO housing (which is connected to the bus bar or circuit board), because here usually only very little structural space is available. In addition, the invention can also be advantageously used for power modules that include multiple parallel chips.

[0014] The proposed method is hardly dependent on the load current and temperature of the DESAT-circuit.

[0015] The invention is applied to semiconductor switches in an inverter circuit for controlling an electric motor (for example as a drive for driving or traction) especially in a vehicle, and exhibits particular advantages because the current flowing through is large and thus the evaluation is simplified. As is well known, an inverter circuit or a rectifier circuit is used to connect the AC voltage connection terminals of an electric motor to the DC voltage connection terminals of a power grid (such as an in-vehicle network) and to convert the voltage accordingly. For this purpose, the inverter circuit has a plurality of semiconductor switches, each of which can be opened (non-conductive) and closed (conductive) according to a control signal. These semiconductor switches can include MOSFETs and IGBTs, such as gallium nitride (GaN) or silicon carbide (SiC) FETs. The in-vehicle network can be a low-voltage power grid or a high-voltage power grid. In the latter case, in order to supply power to the components of the inverter, there is additionally a low-voltage power grid. The high-voltage power grid and the low-voltage power grid can be coupled in the vehicle via a suitable DC voltage converter. For example, the rated voltage level of the high-voltage power grid (hereinafter also referred to as the high-voltage level) can be significantly higher than the permitted touch voltage, especially 60V, for example up to several hundred volts. For example, in current electric vehicles, a high-voltage level of 400V or 800V is often used. For example, the rated voltage level of the low-voltage power grid can correspond to the common vehicle low voltage of, for example, 12V or 24V.

[0016] In one design, the inverter circuit can have a plurality of high-side semiconductor switches and a plurality of low-side semiconductor switches and at least one gate driver for one or more of the corresponding semiconductor switches. The gate driver is used to apply a control signal to the control connection terminal of the semiconductor switch (for example, the gate connection terminal of a MOSFET). The gate driver especially has a DESAT-connection terminal.

[0017] Other advantages and design solutions of the present invention can be obtained from the description and the drawings. Description of the Drawings

[0018] The present invention is schematically illustrated according to the embodiments in the figures and will be described below with reference to the drawings.

[0019] Figure 1 A circuit structure having a semiconductor switch, a gate driver, and a DESAT-circuit is shown, and the present invention can be based on this circuit structure.

[0020] Figure 2a and Figure 2b A sinusoidal load current curve and the associated DESAT-voltage measured in an embodiment of the present invention are shown.

[0021] Figure 3 A partial view of an embodiment of an inverter circuit according to the present invention is shown.

[0022] Figure 4 A partial view of another embodiment of an inverter circuit according to the present invention is shown. Detailed Embodiments

[0023] In Figure 1 the circuit structure is schematically shown and is generally designated by 100, and the present invention starts from this. The circuit structure has a semiconductor switch 10 and a gate driver 20 for controlling (and for monitoring) the semiconductor switch 10. The circuit structure can in particular be part of an inverter circuit.

[0024] The semiconductor switch 10 has a current input connection 10-1, a control connection 10-2, and a current output connection 10-3. The semiconductor switch can have other connections not shown, such as for example a Kelvin source connection etc. Here, the semiconductor switch 10 is shown as a MOSFET or a SiC-MOSFET, and thus the connections are generally and hereinafter referred to as drain, gate, and source. However, the semiconductor switch can also be an IGBT, in which case the connections are generally referred to as collector, gate, and emitter.

[0025] The gate driver 20 includes a connection or pin DESAT, through which the semiconductor switch 10 can be monitored when correctly connected. Only some of the internal components of the gate driver 20 are shown and some are also omitted, but generally, the connection DESAT is connected via (generally internal) current source (here I C ) via the connection VCC2 to a voltage supply (here VCC2), and is connected to a comparator (here an operational amplifier), which compares the voltage V that appears at the DESAT-pin DSATCompared with the internal threshold voltage (here V DSAT_th ), and protection measures are taken according to the comparison result, for example, a circuit with a semiconductor switch (such as a rectifier) is transferred to a safe state.

[0026] Between the current input terminal or drain terminal 10-1 of the semiconductor switch 10 and the DESAT-terminal DESAT of the gate driver 20, a DESAT-circuit 30 is arranged, which has a resistive structural element (hereinafter also simply referred to as a resistor) R DSAT , a blanking capacitor C DSAT and a diode D DSAT . The cathode of the diode is connected to the drain terminal 10-1 of the semiconductor switch 10 to be monitored. It should be noted here that the diode can also be connected in parallel with the drain terminals of multiple semiconductor switches to be monitored. One connection end of the capacitor C DSAT is connected in series with the diode D DSAT and the resistive structural element R DSAT , and the other connection end of the capacitor is grounded.

[0027] If the circuit structure 100 is turned on, the power supply I C charges the blanking capacitor C DSAT , and the diode D DSAT conducts. The current intensity of I C [[ID=?]] can be adjustable, but is also fixedly predetermined in some gate drivers. In normal operation, the voltage of the capacitor is clamped to the voltage on the semiconductor switch 10 via the diode. In case of a short circuit or generally when the load current flowing through the semiconductor switch is very high, the diode becomes non-conductive, and the DESAT-voltage V DSAT appearing at the DESAT-terminal or at the capacitor is then rapidly increased and exceeds the threshold voltage (by a current source), which triggers the DESAT-protection function on the gate drive side and generally causes the semiconductor switch to turn off. This turn-off process can be carried out in a soft turn-off manner to avoid damaging the switch due to the overvoltage occurring during turn-off.

[0028] According to the design of the present invention, in such a circuit structure, the drain-source resistance R DSon can also be derived from the available measured values. In principle, R DSon is obtained through the following formula:

[0029] V DSAT = I C × R DSAT + V F,DSAT + V DSon (1)

[0030] V DSon= V DSAT - I C × R DSAT - V F,DSAT (2)

[0031]

[0032] Wherein, V F,DSAT : the forward voltage of the diode;

[0033] V DSon : drain-source voltage;

[0034] I L : the load current when the semiconductor switch is on (usually measurable);

[0035] I L + I C = I D : drain current (usually not measurable; can be determined if I L and I C are known);

[0036] However, the forward voltage V F,DSAT of the diode and the resistance (value) R DSAT of the structural element are highly temperature-dependent, which has an adverse effect on the accuracy of the calculated value R DSon .

[0037] But if R DSon is determined for two different load current values within a short time interval, the temperature effect can be eliminated.

[0038] Figure 2a In L , the curve of the load current I Figure 2b is schematically shown as a line graph 200 over time t for a typical sinusoidal case (e.g., during the motor operation of a motor), and in DSAT , the relevant values of the measurable DESAT-voltage V n are shown as a line graph 210. For the peak value of the load current at t n+1 and the zero-crossing value at t DSAT , they are marked with the values V n of the DESAT-voltage and V DSAT of the DESAT-voltage at t n+1 .

[0039] Typical inverter circuits usually already have a load or phase current measurement function, so that no additional current sensors are required. However, this sensor can be used in the design of the present invention and is arranged on the load side. For example, assuming a high-voltage power grid here, the output of the sensor must be isolated and then sent to the controller for evaluation, which is usually located in the low-voltage power grid.

[0040] V DSAT It can be measured in the gate driver (see also Figure 3 ) or by an external voltage measurement circuit (see also Figure 4 ); since this measurement is also carried out in the high-voltage power grid, this measurement must also be isolated from the low-voltage power grid.

[0041] The first measurement is carried out at the first moment t n wherein the first drain current I L (t n [[ID=)18]]+I C flows through the semiconductor switch 10. Then the following applies:

[0042]

[0043] wherein the voltage drop V drop (t n ) is

[0044] V drop (t n ) = I C ×R DSAT (t n ) + V F,DSAT (t n ) (5)

[0045] If the first measurement is carried out at the peak point of the current wave, or at a sufficiently large value, or at as large a value as possible, this is beneficial to the signal-to-noise ratio. For example, the first measurement can be carried out at a point with at least 90% or more of the amplitude value.

[0046] In the next step, a measurement is carried out at another moment t n+1 of the load current cycle (see Figure 2). The following applies to this:

[0047]

[0048] V drop (t n+1 ) = I C ×R DSAT (t n+1 ) + V F,DSAT (t n+1) (7)

[0049] In one design, if the second measurement is made at a time when the load current is as small as possible but the semiconductor switch is still conducting, for example, at or near the zero crossing (see Figure 2), the evaluation is very simple because the load current is very low or almost zero at the second time, I L (t n+1 )≈0, and thus the voltage drop across the switch is negligible, that is, V DSon (t n+1 )≈0 (I C is usually very small, for example, in the milliamp range and can thus be neglected at this time).

[0050] In particular, it should be noted that the semiconductor switch 10 is conducting at the first time t n and at the second time t n+1 . It is advantageous to have a situation where the DESAT - voltage determined at the first time t n is greater than the DESAT - voltage determined at the second time t n+1 , especially significantly greater, for example, 100 times or more greater.

[0051] From this, it follows from (1) that:

[0052] V DSAT (t n+1 )=I C ×R DSAT (t n+1 )+V F,DSAT (t n+1 )=V drop (t n+1 ) (8)

[0053] If the durations of the two measurements are very close (for example, at most 1 ms, or at most 10 ms, or at most 25 ms, or at most 50 ms, or at most 100 ms, or at most 1000 ms), it can be assumed that the temperatures of the semiconductor switch, DESAT - diode, and DESAT - resistor structural elements do not change significantly. Therefore, it is expected that V n does not change during two consecutive measurements t n+1 within one electric cycle. Thus, it holds that: drop

[0054]

[0054] V drop (t n )=V drop (t n+1 ) (9)

[0055] From this, V dropThe influence on the measurement, so that it applies:

[0056]

[0057] Thus, for the case where the load current I L (t n+1 )(is basically) zero at the second measurement or at the second moment, from two successive V DSAT measurements (that is, V DSAT (t n ) at the first moment and V DSAT (t n+1 )) at the second moment, the drain-source resistance R L (t n ) for a determined load current I j and a determined barrier layer temperature T DSon (I L (t n ),T j ) is obtained. Since generally I L (t n ) >> I C , so at this time I C can be ignored.

[0058] The temperature characteristic curve of the drain-source resistance R DSon (I L (t n ),T j ), that is, the correlation between the load current and the temperature, can be measured in advance and stored as a table or a family of characteristic curves for a given temperature and load current in a storage device (such as a local non-volatile memory or a remote memory (such as, for example, the cloud)). Therefore, if the drain-source resistance and the related load current are known, the temperature T j can be determined.

[0059] If the temperature T j of the semiconductor switch 10 is higher than the temperature threshold, measures can be taken, such as, for example, reducing the current or turning on, or turning on the semiconductor switch 10 or switching it to blocking, or transferring the circuit with the semiconductor switch (such as a rectifier) to a safe state.

[0060] At Figure 3Fig. 0 schematically shows in the form of a circuit diagram a partial design of an inverter circuit according to an embodiment of the present invention, and is generally designated by 400. The inverter circuit can be used to control, for example, an electric motor (not shown) in a vehicle. The inverter circuit is adapted to monitor a semiconductor switch 10, where the semiconductor switch is arranged together with another semiconductor switch 11 as a so-called low-side switch to form a half-bridge arrangement as a so-called high-side switch. It should be noted, however, that the low-side switch 11 can also be monitored additionally or alternatively.

[0061] The inverter circuit 400 has a gate driver 20, a DESAT-circuit 30, and a controller 410. The controller 410 can be a local controller of the inverter circuit, such as a motor controller (so-called MCU, English "motor control unit", motor control unit), or all data can be transmitted to a remote controller or the cloud and then remotely analyzed. In this example, the use of a local controller is shown.

[0062] The half-bridge arrangement is connected on the supply side to a connection terminal B+ and a connection terminal B-, and these two connection terminals can be supplied, for example, by a DC voltage intermediate circuit and / or the high-voltage power grid of the vehicle. For example, the center tap of the half-bridge arrangement is used as a load connection terminal V OUT and is connected to the stator winding or phase winding of the electric motor.

[0063] By purposefully controlling the semiconductor switches 10 and 11, a desired load current I can be generated in the stator winding L . In the example shown, the load current measurement is achieved by means of a current measurement circuit 420. For example, this current measurement circuit can be connected to a corresponding current sensor 421 in the phase winding or its supply line. Depending on the type of current sensor, for example, if the current sensor 421 is galvanically isolated from the half-bridge arrangement (for example, in the case of a Hall-effect-based current sensor), the current measurement circuit 420 can also be omitted, and the sensor can be directly connected to the controller 410.

[0064] In the controller 410, there is a logic unit 411, and this logic unit programmatically implements the functions of the controller 410.

[0065] The modules for implementing the embodiments of the present invention are shown separately and are especially independent of the logic unit 411. As explained, these modules can also be implemented at other locations or in other controllers. However, implementation in the MCU is advantageous because actually a lot of the required information or data is available here.

[0066] The logic unit 411 determines in particular the PWM signals PWM_1 and PWM_2 for controlling the semiconductor switches 10 and 11. The PWM signals are guided to the input parts IN- and IN+ of the gate driver 20 and to the processing unit 412. The gate driver 20 outputs at the output part OUTH or OUTL a control signal for the semiconductor switch 10 (here independent signals for the input (EIN) and the output (AUS)). The output part is connected via the current limiting resistors R ON and R OFF to the gate 10-2. One or more own gate drivers (not shown) are provided for the semiconductor switch 11, which gate drivers can be constructed and connected like the gate driver 20, or corresponding additional connection terminals (not shown) are provided in the gate driver 20.

[0067] The processing unit 412 is used to acquire different input signals, as shown, which input signals come from, for example, the gate driver 20 and the current measurement circuit 420 or inside the controller 410. To determine the first and second moments suitable for measurement (for example, the peak point and the zero crossing point), the PWM signals PWM_1 and PWM_2 are used. It can also be deduced from the signals PWM_1 and PWM_2 when the semiconductor switch 10 or 11 is conducting or non-conducting.

[0068] The data required for further processing (such as, for example, the load current I L ) is transmitted to the calculation module 414 and / or the temperature determination module 416.

[0069] By means of the digital data interface 413, for example an SPI interface, data can be exchanged digitally between the gate driver 20 and the controller 410, where, in this example, the DESAT-voltage V DSAT . The DESAT-voltage V DSAT is transmitted to the processing unit 412 (for example for synchronization with the current measurement value) and then transmitted to the calculation module 414. As described above, the calculation module calculates from this the drain-source resistance R DSon and transmits it to the temperature determination module 416.

[0070] By means of the processing unit 412 (or the data interface 413), a fault signal (output part Fault) can also be received from the gate driver 20. Subsequently, for further analysis, the fault status of the gate driver can also be read by means of the data interface 413. In the event of a fault or the receipt of a fault signal, the DESAT-value should not be used for monitoring the state of the switch.

[0071] By means of the temperature determination module 416, the current blocking layer temperature T of the semiconductor switch 10 is determined from R DSon and I L ​j .

[0072] In Figure 4 a partial view of another embodiment 500 of the inverter circuit is schematically shown and in the form of a circuit diagram, which substantially corresponds to embodiment 400 according to Figure 3 . Different from the embodiment in Figure 3 , here the DESAT-voltage is not transmitted digitally via the data interface 413 from the gate driver 20, but is measured and transmitted by a separate DESAT-voltage measurement circuit 530.

[0073] As explained, the half-bridge device can be arranged in the high-voltage power grid. On the contrary, the supply of the controller 410 and other modules is realized by the low-voltage power grid in both Figure 3 and Figure 4 . The separation or isolation between the high-voltage power grid and the low-voltage power grid is shown by the dashed lines in the gate driver 20 and the modules forty-two hundred, five hundred and thirty.

Claims

1. A method for determining the temperature (T j ) of a semiconductor switch (10), Among them, The semiconductor switch (10) has a control connection terminal (10-2), a current input connection terminal (10-1), and a current output connection terminal (10-3). Among them, the current input connection terminal (10-1) is connected to the potential connection terminal (VCC2) via a diode (D DSAT ), a connection end point of a capacitor (C DSAT ), a resistor structural element (R DSAT ), and a current source (I C ). Among them, the other connection end of the capacitor (C DSAT ) is grounded. The method includes the following steps: a) Determine the DESAT - voltage (V n ) that appears at the capacitor (C n+1 ) at a first time (t DSAT ) and a second time (t DSAT ); b) Determine the load current (I n ) flowing between the current input connection terminal (10-1) and the current output connection terminal (10-3) of the semiconductor switch (10) at the first moment (t L ); c) Determine the drain-source resistance (R n ) existing between the current input connection terminal (10-1) and the current output connection terminal (10-3) of the semiconductor switch (10) at the first moment (t n+1 ) from the DESAT-voltage (V DSAT ) and the load current (I L ) determined at the first moment (t n ) and the second moment (t DSon ); d) Determine the temperature (T DSon ) of the semiconductor switch (10) from the drain-source resistance (R L ) and the load current (I j ).

2. The method according to claim 1, wherein The DESAT voltage (V DSAT ) occurring at the capacitor (C DSAT ) is acquired by means of the DESAT voltage measurement circuit (530).

3. The method according to claim 1 or 2, wherein The current input connection terminal (10-1) is connected to the DESAT-connection terminal (DESAT) of the gate driver (20) via the diode (D DSAT ), the connection end point of the capacitor (C DSAT ), and the resistive structural element (R DSAT ), wherein the DESAT-connection terminal (DESAT) of the gate driver (20) is connected to the potential connection terminal (VCC2) via the current source (I C ) of the gate driver (20).

4. The method according to claim 3, wherein, Determine the DESAT voltage (V DSAT ) that occurs at the capacitor (C DSAT ) within the gate driver (20).

5. The method according to any one of the preceding claims, wherein, The semiconductor switch (10) is turned on at the first moment (t n ) and the second moment (t n+1 ).

6. The method according to any one of the above claims, wherein Between the first moment (t n ) and the second moment (t n+1 ), there is at most 1 ms or at most 10 ms or at most 25 ms or at most 50 ms or at most 100 ms or at most 1000 ms.

7. The method according to any one of the preceding claims, wherein, The DESAT-voltage (V n ) determined at the first moment (t DSAT ) is greater than the DESAT-voltage (V n+1 ) determined at the second moment (t DSAT ).

8. The method according to any one of the preceding claims, wherein, Said second moment (t n+1 ) corresponds to the moment when the current is as small as possible or when the load current curve (200) passes through zero.

9. The method according to any one of the preceding claims, wherein The first moment (t n ) corresponds to the moment when the current is as large as possible or the peak moment of the load current curve (200).

10. The method according to any one of the preceding claims, wherein, Determine the temperature (T DSon ) of the semiconductor switch (10) from the drain-source resistance (R L ) and the load current (I j ) by means of a family of characteristic curves.

11. The method according to any one of the preceding claims further includes: If the temperature (T j ) of the semiconductor switch (10) is higher than a temperature threshold, measures are taken.

12. The method according to any one of the preceding claims, wherein, Determine the temperature (T j ) of the high-side switch and / or the low-side switch of the half-bridge device.

13. An inverter circuit (400) for controlling an electric machine, the inverter circuit having at least one semiconductor switch (10) and a controller (410), wherein, The inverter circuit (400) is adapted to perform the method according to any one of the preceding claims.

14. The inverter circuit according to claim 13, wherein the inverter circuit has a gate driver (20), and the gate driver has a DESAT connection terminal (DESAT), where The current input connection terminal (10-1) of the semiconductor switch (10) is connected to the DESAT connection terminal (DESAT) of the gate driver (20) via the diode (D DSAT ), the connection end point of the capacitor (C DSAT ) and the resistive structural element (R DSAT ), wherein the DESAT connection terminal (DESAT) of the gate driver (20) is connected to the potential connection terminal (VCC2) via the current source (I C ).

15. The inverter circuit according to claim 13, wherein the inverter circuit further has a DESAT-voltage measurement circuit (530) for determining the DESAT-voltage (V DSAT ), and the DESAT-voltage measurement circuit is connected to the controller (410).

16. The inverter circuit according to claim 13, wherein, The gate driver (20) is connected to the controller (410) via a digital data interface (413) for transmitting the DESAT-voltage (V DSAT ).

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