Method and device for discharging the intermediate circuit of an inverter

Abstract

A device for discharging the intermediate circuit of the inverter of an electric drive system of a vehicle is described. The device is configured to determine that the intermediate circuit of the inverter is to be discharged. Furthermore, the device is configured, in response to this determination, to increase the switching losses caused by one or more switching elements of the inverter during a switching operation compared to normal operation of the inverter.

Description

[0001] The invention relates to a method and a corresponding device, each designed to discharge the intermediate circuit of an inverter.

[0002] An electrically powered vehicle has at least one electric drive motor, such as a current-excited synchronous machine, as part of its electric drive system. The multiphase alternating current required to operate the electric drive motor can be generated from the direct current supplied by the vehicle's electrical energy storage system using an inverter. The inverter typically includes several semiconductor-based switching elements, particularly MOSFETs. Furthermore, the inverter typically includes a DC link, with one or more DC link capacitors, to stabilize the DC voltage.

[0003] In the event of a safety-related incident, it may be necessary to discharge the intermediate circuit in order to bring the vehicle's electric drive system into a safe state.

[0004] This document addresses the technical task of achieving efficient and reliable discharge of the intermediate circuit of an inverter.

[0005] The problem is solved by each of the independent claims. Advantageous embodiments are described, inter alia, in the dependent claims. It should be noted that additional features of a claim dependent on an independent claim, without the features of the independent claim itself or only in combination with a subset of the features of the independent claim, can constitute a separate invention independent of the combination of all features of the independent claim, which can be made the subject of an independent claim, a divisional application, or a subsequent application. This applies equally to technical teachings described in the description, which can constitute an invention independent of the features of the independent claims.

[0006] According to one aspect, a device for discharging the intermediate circuit of the inverter of an electric drive system of a (motor) vehicle is described. The drive system can include the inverter and an electric (drive) machine (in particular a synchronous machine) downstream of the inverter. The inverter can include several (semiconductor-based) switching elements. The switching elements can be arranged in several (semiconductor) bridges for several phases of the electric machine. The switching elements of each bridge can generate the phase voltage and / or the phase current of the respective phase of the electric machine.

[0007] The device can be configured to operate the inverter's switching elements during normal operation such that alternating voltages (i.e., the phase voltages) are generated based on the DC voltage applied to the intermediate circuit for the operation of the electric machine of the vehicle's electric drive system. During normal operation, the switching elements are preferably operated in such a way as to achieve the lowest possible switching losses during each individual switching operation.

[0008] The device is designed to determine when the inverter's intermediate circuit needs to be discharged (e.g., due to a vehicle accident and / or due to upcoming vehicle maintenance).

[0009] The device is further configured to increase, in response to a specified setting, the switching losses caused by one or more switching elements of the inverter during each switching operation, compared to the inverter's normal operation. It can thus be specifically designed to selectively increase the switching losses during the switching operations of one or more switching elements for the purpose of discharging the DC link (e.g., by 5% or more, or by 10% or more, or by 20% or more). This allows for particularly efficient and reliable discharge of the DC link (possibly without the use of an additional discharge circuit).

[0010] The device can be configured to operate a (specific) switching element of the inverter during normal operation in such a way that initial switching losses occur during a switching operation of the (specific) switching element. Furthermore, the device can be configured to operate the (specific) switching element of the inverter for discharging the intermediate circuit in such a way that secondary switching losses occur during a switching operation of the (specific) switching element, wherein the secondary switching losses are greater, in particular by 20% or more, than the primary switching losses.

[0011] Alternatively or additionally, the device can be configured to cause a (specific) switching element of the inverter to perform a switching operation at a first switching speed during normal operation of the inverter. Furthermore, the device can be configured to cause the (specific) switching element of the inverter to perform a switching operation at a second switching speed for the purpose of discharging the inverter's intermediate circuit, wherein the first switching speed is higher, in particular by 20% or more, than the second switching speed.

[0012] Alternatively or additionally, the device can be configured to control a (specific) switching element of the inverter via a first control resistor during normal operation of the inverter. Furthermore, the device can be configured to control the (specific) switching element of the inverter via a second control resistor for discharging the intermediate circuit of the inverter, wherein the second control resistor has a resistance value that is greater, in particular by 10% or more or by 20% or more, than the resistance value of the first control resistor.

[0013] It should be noted that the inverter's switching element can be controlled stepwise and / or sequentially via N different control resistors, with N ≥ 2, and in particular with N ≥ 3 or N ≥ 4. The resistance value of each control resistor can be increased stepwise. This document describes a first and a second control resistor as examples. However, the described aspects are generally applicable to N different control resistors.

[0014] The device can thus be configured, in response to the determination that the intermediate circuit of the inverter is to be discharged, to cause that • the switching speed of switching operations of one or more switching elements of the inverter is reduced compared to normal operation, in particular by at least 10% or at least 20%; and / or • the resistance value of a control resistor for controlling one or more switching elements of the inverter is increased compared to normal operation, in particular by at least 10% or at least 20%.

[0015] By selectively adjusting the switching speed and / or the resistance value of the control resistor, a particularly efficient and reliable discharge of the intermediate circuit can be achieved.

[0016] The device can include a microprocessor with a first pin and a second pin. Generally, the microprocessor can have N different pins (for N different control resistors), with N ≥ 2, and in particular with N ≥ 3 or N ≥ 4. The first pin can be used to control a (specific) switching element during normal operation. The second pin (or the N-1 additional pins) can be used to control the (specific) switching element for discharging the DC link. By using dedicated pins for normal operation and for discharging the DC link, particularly reliable operation of the inverter can be achieved.

[0017] The device can be configured, in particular, to control the (specific) switching element of the inverter via a first line with the first control resistor during normal operation of the inverter, wherein the first power supply is coupled to the first pin of the microprocessor in order to effect the control current for a switching operation of the (specific) switching element via the first pin (and not via the second pin). Furthermore, the device can be configured to control the (specific) switching element of the inverter via a second line with the second control resistor for discharging the intermediate circuit of the inverter, wherein the second line is coupled to the second pin of the microprocessor in order to effect the control current for a switching operation of the (specific) switching element via the second pin (and not via the first pin).

[0018] The device can be configured to detect when a first switching element of the inverter has reached a predefined thermal state, in particular a predefined temperature threshold, due to increased switching losses associated with discharging the inverter's DC link. In response to this detection, at least one other switching element of the inverter can then be used instead of the first switching element to discharge the inverter's DC link through one or more switching operations with increased switching losses. By thermally monitoring the different switching elements (and / or the drivers for the different switching elements), a particularly reliable discharge of the DC link can be achieved.One or more other switching elements can be used to discharge the intermediate circuit if the temperature of the first switching element reaches or exceeds the predefined temperature threshold.

[0019] The inverter can comprise N groups of multiple switching elements, with N ≥ 2, where the switching elements of a group can each be configured to cause an active short circuit of the different phases of the inverter. For example, the high-side switching elements of the inverter can form one group, and the low-side switching elements of the inverter can form another group.

[0020] The device can be configured to discharge the inverter's DC link by inducing switching operations of (in particular, all) switching elements from exactly one group of switching elements, such that the switching elements of that group cause an active short circuit. Furthermore, the device can be configured to discharge the inverter's DC link by sequentially inducing switching operations of (in particular, all) switching elements from different groups of switching elements, such that the switching elements of each different group selectively cause an active short circuit.Thus, switching elements from different groups of switching elements can be used sequentially to create an active short circuit (to bring the drive system into a safe state) and thereby cause increased switching losses (to discharge the DC link). In this way, the electric drive system can be brought into a safe state in a particularly efficient and reliable manner.

[0021] As previously explained, the inverter typically has at least one (half-)bridge with several switching elements, the bridge being arranged between different poles of the DC link. Typically, the inverter has one bridge with switching elements for each phase of the electric machine. The device can be configured to cause switching operations of the bridge's switching elements to discharge the inverter's DC link, so that the switching elements (temporarily) cause a bridge short circuit between the different poles of the DC link. By causing a bridge short circuit, the DC link can be discharged in a particularly efficient and reliable manner.

[0022] According to another aspect, a (road) motor vehicle (in particular a passenger car or a truck or a bus or a motorcycle) is described that includes the device described in this document.

[0023] According to one aspect, a method for discharging the DC link of the inverter of an electric drive system of a (motor) vehicle is described. The method includes determining that the DC link of the inverter must be discharged (e.g., to bring the drive system into a safe (de-energized) state).

[0024] The method further comprises, in response to the determination, causing the switching losses caused by one or more switching elements of the inverter during (each) a switching operation (of the respective switching element) to be increased compared to the normal operation of the inverter (in which the switching elements are operated for generating the phase voltages and / or phase currents of the electrical machine of the drive system).

[0025] It should be noted that the aspects described in connection with the device, in particular the claims described in connection with the device, are also applicable to the method as corresponding process features.

[0026] Another aspect described is a software (SW) program. The SW program can be configured to run on a processor (e.g., on a vehicle's control unit) and thereby execute the procedure described in this document.

[0027] Another aspect describes a storage medium. This storage medium can include a software program configured to run on a processor and thereby execute the procedure described in this document.

[0028] It should be noted that the methods, devices, and systems described in this document can be used both alone and in combination with other methods, devices, and systems described in this document. Furthermore, any aspect of the methods, devices, and systems described in this document can be combined with one another in a variety of ways. In particular, the features of the claims can be combined with one another in a variety of ways. Features listed in parentheses are to be understood as optional features.

[0029] The invention will now be described in more detail using exemplary embodiments. Fig. 1a Exemplary components of a vehicle with an electric drive motor; Fig. 1b an example inverter; Fig. 2a an exemplary control circuit for a switching element; Fig. 2b Exemplary switching losses of a switching element; Fig. 2c the exemplary slope of the control current in normal operation and in operation with increased switching losses; Fig. 2d the exemplary switching speed of a switching element in normal operation and in operation with increased switching losses; and Fig. 3 A flowchart of an exemplary procedure for discharging the intermediate circuit of an inverter.

[0030] As stated at the beginning, this document deals with the efficient and reliable discharge of the intermediate circuit of an inverter. In this context, it shows Fig. 1a Exemplary components of a vehicle 140, which includes an electric machine 103 for propelling the vehicle 140. The electric machine 103 is coupled to one or more wheels 141 of the vehicle 140 to drive the one or more wheels 141 and thus the vehicle 140. The electric machine 103 is operated with electrical energy from an electrical, in particular an electrochemical, energy storage device 130. The energy storage device 130 can be configured to provide a direct current with a specific direct voltage (e.g., of 300 V or more).

[0031] The vehicle 140 has an inverter 100, which is configured to generate phase currents for the different phases of the electric machine 103 based on the direct current from the energy storage device 130. The inverter 100 can be operated by a (control) device 101. The inverter 100 and the electric machine can be part of the electric drive or the electric drive system of a vehicle 140.

[0032] Fig. Figure 1b shows an exemplary inverter 100 configured to generate phase voltages 111 (i.e., alternating voltages) for the inductors of the electric machine 103 based on an intermediate circuit voltage 110 (i.e., a DC voltage). The drive may further include an intermediate circuit 105 with an intermediate circuit capacitor to which the intermediate circuit voltage 110 is applied.

[0033] The inverter 100 comprises several switching elements 102, 104, which in the illustrated example are arranged in a half-bridge for each phase 121, 122, 123. The switching elements 102, 104 are controlled by the (control) device 101 to generate the phase voltages 111 for the electric machine 103. The individual phase currents 112 and / or phase voltages 111 can be supplied to the electric machine 103 via corresponding phase lines.

[0034] The (control) device 101 of the vehicle 140 can be configured to determine that the electric drive system of the vehicle 140 is to be brought into a safer state (e.g., due to an accident involving the vehicle 140). In this context, it may be necessary to reduce the amount of electrical energy stored in the drive system, in particular in the electric machine 103 and / or in the DC link 105. Furthermore, it may be necessary to decouple the electrical energy storage device 130 from the inverter 100, in particular from the DC link 105. For this purpose, one or more isolating elements, e.g., relays (not shown), can be opened.

[0035] To bring the electric drive system into a safe state, the inverter 100 can create an active short circuit between the different phases 121, 122, 123. Simultaneously, the high-side switching elements 102 or (alternatively) the low-side switching elements 104 of the inverter 100 can be closed. As a result, the phase terminals of the electric machine 103 are short-circuited together, causing equalizing currents between the different phases 121, 122, 123 and an equalization of the phase voltages 111.

[0036] The electrical energy stored in the intermediate circuit 105, particularly in the one or more intermediate circuit capacitors of the intermediate circuit 105, can be reduced, and in particular converted into thermal energy, by using a dedicated discharge circuit. The discharge circuit can include one or more ohmic discharge resistors. However, the use of a dedicated discharge circuit leads to an increased hardware complexity in the electric drive system of the vehicle 140.

[0037] Switching losses occur during the individual switching operations of the switching elements 102, 104 of the inverter 100. During normal operation of the inverter 100, these switching losses should typically be kept as low as possible, which can be achieved in particular by a relatively high slew rate of the control current for controlling the switching elements 102, 104 and a resulting relatively high switching speed of the switching elements 102, 104.

[0038] On the other hand, the switching losses caused during the switching operations of the switching elements 102, 104 can be used in a special operation of the inverter 100 to discharge the intermediate circuit 105 of the inverter 100, in particular to bring the electric drive system of the vehicle 100 into a safe state.

[0039] Fig. Figure 2a shows an exemplary control circuit 200 for a switching element 210, 102, 104 (of the inverter 100). The control circuit 200 comprises a control device 203 (in particular a gate driver) configured to generate a control current for controlling the switching element 210. The control current can be routed via a line to the control port G, in particular to the gate, of the switching element 210. At least one control resistor 201, 202 (in particular a gate resistor) can be arranged across the line between the control device 203 and the control port 210. Depending on the polarity of the control current, the switching element 210 can be switched from the open state to the closed state or from the closed state to the open state.For example, a control current into control port G can cause a transition to the closed state, and a control current out of control port G can cause a transition from the closed state to the open state. Alternatively, the relationship between the polarity of the control current and the resulting state of the switching element 210 can be exactly reversed.

[0040] The in Fig. The control circuit 200 shown in Figure 2a comprises a first control resistor 201 with a first resistance value and a second control resistor 201 with a second resistance value, the first resistance value being smaller than the second resistance value. In general, the control circuit 200 can have N control resistors with different resistance values, where N ≥ 2. The control device 203 can be configured to ensure that, during normal operation of the inverter 100, the control current is routed through the first control resistor 201 (and not through the second control resistor 202). The relatively small initial resistance value of the first control resistor 201 results in a relatively high slew rate of the control current and, consequently, a relatively high switching speed of the switching element 210.In normal operation of the inverter, 100 energy-efficient switching operations of one or more switching elements 210, 102, 104 of the inverter 100 can be effected.

[0041] The control device 203 can further be configured to ensure that, in the special operating mode of the inverter 100, the control current is routed to the control port G of the switching element 210 via the second control resistor 202 (and not via the first control resistor 201). The relatively high resistance of the second control resistor 202 results in a relatively low slew rate of the control current and, consequently, a relatively low switching speed of the switching element 210. Thus, in the special operating mode of the inverter 100, switching operations of one or more switching elements 210, 102, 104 of the inverter 100 can be performed with a relatively high power dissipation. This increased power dissipation can be used for accelerated discharge of the intermediate circuit 105.

[0042] Fig. Figure 2b shows, by way of example, the switching losses 222 of a switching element 210 in different operating phases. It should be noted that the transitions between the different operating phases typically involve (gradual) changes in the switching losses 222. In a first operating phase up to time 225, the switching element 210 can be controlled (for normal operation) via the first control resistor 201 with its relatively low resistance value, resulting in relatively low switching losses 222. Conversely, in a second operating phase from time 225 to time 226, the switching element 210 can be controlled via the second control resistor 202 with its relatively low resistance value, resulting in relatively high switching losses 222.

[0043] Fig. Figure 2c shows exemplary edge slew rates of the control current 230 for controlling the switching element 210 in the different operating phases. In the first operating phase (i.e., in normal operation), a switching operation typically involves a relatively high edge slew rate (i.e., edge 231 has a relatively high slew rate or (in magnitude) a relatively high gradient), while in the second operating phase (to increase switching losses), a switching operation typically involves a relatively low edge slew rate (i.e., edge 232 has a relatively low slew rate or (in magnitude) a relatively low gradient).

[0044] Fig. Figure 2d shows exemplary switching speeds 242 of the switching element 210 in the different operating phases. In the first operating phase, a relatively high switching speed 242 is typically present, while in the second operating phase, a relatively low switching speed 242 is typically present.

[0045] It can thus be ensured that the switching losses 222 of one or more switching elements 210, 102, 104 of the inverter 100 are increased specifically for the discharge of the intermediate circuit 105. Repeated switching operations between the open and closed states can be effected. These switching operations can be performed within the context of an active short circuit of the inverter 100. For example, all high-side switching elements 210, 102 or (alternatively) all low-side switching elements 210, 104 can be closed alternately (and possibly repeatedly).

[0046] As already explained, the switching of the gate drivers of the switching elements 102, 104 of the inverter 100 and the subsequent switching of the switching elements 102, 104 of the inverter 100 are controlled by control signals from a control device 203 (in particular a microcontroller). In normal operation, it is typically advantageous to select the input resistances 201 of the gate drivers as low as possible in order to achieve fast switching speeds (current increase and / or voltage drop) of the switching elements 102, 104 (taking into account EMC (electromagnetic compatibility) requirements).

[0047] By means of an additional control signal (e.g., via another pin of the microcontroller), a relatively high input resistance 202 can be generated and / or used at the gate drivers, leading to relatively long switching times (i.e., relatively low switching speeds) of the switching elements 102, 104. These long switching times increase the power losses of the gate drivers and the switching operations of the switching elements 102, 104. Due to the increased switching losses 222, the DC link 105 of the inverter 100 can be discharged more quickly.

[0048] The control device 203 can be configured to detect when the gate driver of a switching element 102, 104 exceeds a defined thermal limit due to the relatively long switching time. It can then cause another switching element 102, 104 of the inverter 100 to be used to discharge the DC link 105. In a 2-level inverter 100, switching is possible between the high-side switching elements 102 and the low-side switching elements 104. In a 3-level inverter 100, switching is possible between high-side switching elements 102, midpoint switching elements, and low-side switching elements 104, or, in an N-level inverter, between N different switching elements (with N ≥ 2).

[0049] The generation of increased switching losses 222 can be integrated into the active short circuit (ACC) function. If necessary, a bridge short circuit can also be deliberately (at least temporarily) generated to discharge the DC link 105. In the case of an ACC, the short circuit can be interrupted relatively briefly to switch between the different groups of switching elements 102, 104 (and thereby generate the switching losses 222 to discharge the DC link 105). Groups of (e.g., 3 or 6) switching elements 102, 104 can be controlled simultaneously, so that the switching losses 222 can be increased accordingly.

[0050] To avoid the risk of overheating the gate drivers and / or the switching elements 102, 104, it is possible to switch between different gate drivers or switching elements 102, 104, so that unused gate drivers and / or switching elements 102, 104 can cool down during discharge.

[0051] Fig. Figure 3 shows a flowchart of a (possibly computer-implemented) method 300 for discharging the intermediate circuit 105 of an inverter 100 of an electric drive system of a (motor) vehicle 140. The method 300 can be executed by a control device 101, 203 of the vehicle 140. The intermediate circuit 105 can include one or more intermediate circuit capacitors.

[0052] Procedure 300 includes determining 301 that the intermediate circuit 105 of the inverter 100 needs to be discharged. For example, it may be detected that the vehicle 140 has been in an accident or that the vehicle 140 requires maintenance. Based on this, it can be determined that the intermediate circuit 105 needs to be discharged (in order to bring the electric drive system into a safe state).

[0053] Furthermore, in response to determining 301, the method 300 comprises causing 302 the switching losses 222 caused by one or more switching elements 102, 104 of the inverter 100 during (at least) one switching operation to be increased compared to the normal operation of the inverter 100 (in which the inverter 100 is operated to generate the phase voltages 111 and / or the phase currents 112 for the electrical machine 103).

[0054] Within the framework of procedure 300, one or more further process steps can be carried out. In particular, the DC link voltage 110 (i.e., the value of the DC link voltage 110) can be determined (e.g., in response to the determination 301). Based on the determined DC link voltage 110, the required discharge power and / or the amount of discharge energy for discharging the DC link 105 can be determined. Based on this, one or more parameters for the discharge process for discharging the DC link 105 can be determined. Example parameters are: • one or more control points for controlling one or more switching elements 210, 102, 104 (which are used to discharge the intermediate circuit 105); • a number of switching cycles of one or more switching elements 210, 102, 104 for discharging the intermediate circuit 105; and / or • a number of switching elements 201, 102, 104 that are switched simultaneously and / or sequentially (to discharge the intermediate circuit 105).

[0055] During the discharge process (particularly within the framework of method 300), the thermal state, especially the temperature, of one or more switching elements 210, 102, 104 (used for discharging the intermediate circuit 105) can be monitored. If necessary (depending on the thermal state monitoring), the one or more switching elements 210, 102, 104 used for discharging the intermediate circuit 105 can be changed.

[0056] As part of thermal monitoring, the temperature of one or more switching elements 210, 102, 104 can be predicted in order to trigger an early change (before exceeding the permissible temperature threshold) of the one or more switching elements 201, 102, 104 used for the discharge process. The temperature prediction can be based on a thermal model of the one or more switching elements 210, 102, 104.

[0057] The measures described in this document enable the intermediate circuit 105 of the inverter 100 of an electric drive system of a vehicle 140 to be discharged in an efficient and reliable manner.

[0058] The present invention is not limited to the embodiments shown. In particular, it should be noted that the description and the figures are intended only to illustrate the principle of the proposed methods, devices, and systems by way of example.

Claims

[1] Device (101, 203) for discharging an intermediate circuit (105) of an inverter (100) of an electric drive system of a vehicle (140); wherein the device (101, 203) is configured, - to determine that the intermediate circuit (105) of the inverter (100) is to be discharged; and - in response to the determination to cause switching losses (222) caused by one or more switching elements (102, 104) of the inverter (100) during a switching operation to be increased compared to normal operation of the inverter (100). [2] Device (101, 203) according to claim 1, wherein the device (101, 203) is configured, - in the normal operation of the inverter (100) a switching element (102, 104) of the inverter (100) is operated in such a way that initial switching losses (222) are caused during a switching operation of the switching element (102); and - to discharge the intermediate circuit (105) of the inverter (100) the switching element (102, 104) of the inverter (100) is operated in such a way that during a switching operation of the switching element (102) second switching losses (222) are caused; wherein the second switching losses (222) are greater, in particular by 20% or more greater, than the first switching losses (222). [3] Device (101, 203) according to one of the preceding claims, wherein the device (101, 203) is configured, - to cause a switching element (102, 104) of the inverter (100) to perform a switching operation with a first switching speed during normal operation of the inverter (100); and - to discharge the intermediate circuit (105) of the inverter (100) by causing the switching element (102, 104) of the inverter (100) to perform a switching operation with a second switching speed; wherein the first switching speed is higher, in particular by 20% or more, than the second switching speed. [4] Device (101, 203) according to one of the preceding claims, wherein the device (101, 203) is configured, - to control a switching element (102, 104) of the inverter (100) via a first control resistor (201) during normal operation of the inverter (100); - to discharge the intermediate circuit (105) of the inverter (100) by controlling the switching element (102, 104) of the inverter (100) via a second control resistor (202); wherein the second control resistor (202) has a resistance value that is greater, in particular by 20% or more, than the resistance value of the first control resistor (201). [5] Device (101, 203) according to one of the preceding claims, wherein the device (101, 203) is configured to cause, in response to the determination that the intermediate circuit (105) of the inverter (100) is to be discharged, that - the switching speed of switching operations of one or more switching elements (102, 104) of the inverter (100) is reduced compared to normal operation, in particular by at least 10%; and / or - the resistance value of a control resistor (202) for controlling one or more switching elements (102, 104) of the inverter (100) is increased compared to normal operation, in particular by at least 10%. [6] Device (101, 203) according to one of the preceding claims, wherein the device (101, 203) comprises a microprocessor having a first pin and a second pin, and wherein the device (101, 203) is configured, - in the normal operation of the inverter (100) to control a switching element (102, 104) of the inverter (100) via a first line with a first control resistor (201), wherein the first power is coupled to the first pin of the microprocessor in order to effect a control current for a switching operation of the switching element (102, 104) via the first pin; and - to discharge the intermediate circuit (105) of the inverter (100) the switching element (102, 104) of the inverter (100) is controlled via a second line with a second control resistor (202), wherein the second line is coupled to the second pin of the microprocessor in order to effect a control current for a switching operation of the switching element (102, 104) via the second pin. [7] Device (101, 203) according to one of the preceding claims, wherein the device (101, 203) is configured, - to recognize that a first switching element (102) of the inverter (100) has reached a predefined thermal state, in particular a predefined temperature threshold, due to the increased switching losses (222) for discharging the intermediate circuit (105) of the inverter (100); and - in response to the detection, to cause a different second switching element (104) of the inverter (100) to be used instead of the first switching element (102) of the inverter to discharge the intermediate circuit (105) of the inverter (100) by means of one or more switching operations with increased switching losses (222). [8] Device (101, 203) according to one of the preceding claims, wherein - the inverter (100) comprises N groups of several switching elements (102, 104) each, with N≥2; - the switching elements (102, 104) of a group are each configured to cause an active short circuit of different phases (121, 122, 123) of the inverter (100); and - the device (101, 203) is set up to discharge the intermediate circuit (105) of the inverter (100) by causing switching operations of the switching elements (102, 104) from each of the groups of switching elements (102, 104) so ​​that an active short circuit is caused by the switching elements (102, 104) of this group of switching elements (102, 104). [9] Device (101, 203) according to claim 8, wherein the device (101, 203) is configured to discharge the intermediate circuit (105) of the inverter (100) by sequentially effecting switching operations of the switching elements (102, 104) from different groups of switching elements (102, 104), such that an active short circuit is selectively caused sequentially by the switching elements (102, 104) from different groups of switching elements (102, 104). [10] Device (101, 203) according to one of the preceding claims, wherein - the inverter (100) comprises at least one bridge with several switching elements (102, 104), wherein the bridge is arranged between different poles of the intermediate circuit (105); and - the device (101, 203) is set up to discharge the intermediate circuit (105) of the inverter (100) by causing switching operations of the switching elements (102, 104) of the bridge, so that the switching elements (102, 104) cause a bridge short circuit of the different poles of the intermediate circuit (105). [11] Device (101, 203) according to one of the preceding claims, wherein the device (101, 203) is configured to operate the switching elements (102, 104) of the inverter (100) in normal operation such that alternating voltages (111) are generated on the basis of a DC voltage (110) applied to the intermediate circuit (105) for the operation of an electric machine (103) of the electric drive system of the vehicle (140). [12] Method (300) for discharging an intermediate circuit (105) of an inverter (100) of an electric drive system of a vehicle (140); wherein the method (300) comprises, - Determine (301) that the intermediate circuit (105) of the inverter (100) is to be discharged; and - in response to determining (301), causing (302) that switching losses (222) caused by one or more switching elements (102, 104) of the inverter (100) during a switching operation are increased compared to normal operation of the inverter (100).

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