Monitoring device and method for monitoring closed state of battery switch, converter device, bridge drive and motor vehicle

Abstract

The invention relates to a monitoring device and a method for monitoring the closed state of a battery switch, a converter device, a bridge drive and a motor vehicle. A monitoring device (100) for monitoring a closed state of a battery switch (105) has an energy source (140), a diode (130) connected in series with the energy source, and an evaluation circuit (150). The energy source (140) and the diode (130) are connected in parallel with the battery switch (105). The energy source (140) is configured for generating a current flow or a voltage between a first switch terminal (106) of the battery switch (105) and a second switch terminal (108) of the battery switch (105). The evaluation circuit (150) is designed to provide an evaluation signal (195) indicative of a closed state of the battery switch (105) by using an electrical potential that can be tapped between the diode (130) and the energy source (140).

Description

Technical Field

[0001] The invention relates to a closed state monitoring device and method for monitoring a battery switch, a converter device, an electric vehicle axle drive and a motor vehicle. Background Art

[0002] The intermediate circuit of the converter can be discharged by passive discharge or active discharge. A battery switch can be arranged between the battery and the intermediate circuit. Summary of the invention

[0003] Against this background, the invention provides, according to the independent claims, an improved monitoring device and an improved method for monitoring the closed state of a battery switch, an improved converter device, an improved electric vehicle axle drive and an improved motor vehicle. Advantageous embodiments emerge from the dependent claims and the following description.

[0004] The advantages that can be achieved with the approach presented here are particularly evident in that the monitoring device provided can reliably and quickly monitor the closed state of the battery switch.

[0005] The monitoring device is configured to monitor a closed state of a battery switch. The battery switch has a first switch terminal for connecting the battery switch to an electrode of a battery and a second switch terminal for connecting the battery switch to an electrode of an intermediate circuit. The monitoring device has a series circuit consisting of an energy source and a diode, and also has an evaluation circuit. The series circuit is connected in parallel with the battery switch. The energy source has a first energy source terminal and a second energy source terminal. The energy source is configured to generate a current flow or a voltage between the first switch terminal and the second switch terminal of the battery switch. The diode has a first diode terminal and a second diode terminal. The first diode terminal is connected to the second energy terminal. The evaluation circuit is configured to provide an evaluation signal indicating the closed state of the battery switch by using a potential present at the first diode terminal.

[0006] For example, by identifying the closed state of the battery switch, it can be confirmed whether the instruction for disconnecting the battery as an energy storage device from the intermediate circuit has been successfully executed. This can provide the advantage of actively discharging the intermediate circuit. Therefore, the solution introduced here can also be understood as monitoring of battery disconnection.

[0007] The battery switch can be arranged in a circuit connecting the battery and the intermediate circuit according to known battery switches. The electrodes of the battery and the electrodes of the intermediate circuit can represent either two positive poles or two negative poles according to different embodiments. By using an energy source, a test voltage can be applied to the battery switch, or a test current can be conducted through the battery switch so that a closed state can be identified. It can be fully utilized here that the magnitude of the potential caused by the test voltage or the test current at the interception point (for example, the connection position between the diode and the energy source) is related to the closed state of the battery switch and is thus suitable for generating an evaluation signal. Here, the evaluation circuit can be configured to provide an evaluation signal with a first value (the first value represents the closed state of the battery switch) or an evaluation signal with a second value (the second value represents the disconnected state of the battery switch) depending on the magnitude of the potential occurring at the interception point.

[0008] The diode can have a cathode and an anode. The first diode terminal can be the anode and the second diode terminal can be the cathode. By setting the polarity of the diode accordingly, the battery voltage of the battery can be blocked.

[0009] The evaluation circuit may include a comparator. The comparator has a first input, a second input, and an output. The comparator may be connected to the first diode terminal via the first input and to the reference voltage terminal via the second input. The comparator may be configured to provide an evaluation signal at the output. The comparator may reliably and quickly compare a potential associated with the closed state of the battery switch with a reference potential of the reference voltage terminal.

[0010] The first energy source terminal can be connected to the second switch terminal, and the second diode terminal can be connected to the first switch terminal. This embodiment is advantageous when the battery switch is arranged between the positive pole of the battery and the positive pole of the intermediate circuit.

[0011] Alternatively, the first energy source terminal can be connected to the first switch terminal and the second diode terminal can be connected to the second switch terminal. This embodiment is advantageous when the battery switch is arranged between the negative pole of the battery and the negative pole of the intermediate circuit.

[0012] The energy source can be designed as a current source.

[0013] Alternatively, the energy source can be designed as a voltage source. This simplifies the selection of a suitable energy source.

[0014] The energy source may have a first resistor, a second resistor and a supply potential. The first resistor may be connected between the supply potential and a second energy source terminal of the energy source. The second resistor may be connected between the first energy source terminal and the second energy source terminal. In this way, the energy source may be easily constructed as a voltage source with a resistor divider.

[0015] The series circuit may have a third resistor. The third resistor may be integrated at a suitable location of the series circuit. The third resistor may be implemented with high resistance, so as to enable safe operation of the monitoring device, for example when a recovery is expected.

[0016] A diode may be connected between the third resistor and the energy source. This makes reliable operation of the monitoring device possible.

[0017] The monitoring device may have a battery switch. The battery switch may include a first switch terminal for connecting the battery switch to an electrode of the battery and a second switch terminal for connecting an electrode of the battery switch to an electrode of the intermediate circuit. For example, the monitoring device including the battery switch may be provided as a circuit unit.

[0018] A converter device has an embodiment of the monitoring device mentioned here. In addition, the converter device also has an intermediate circuit and a converter device for converting the battery voltage into a drive voltage. The intermediate circuit is connected between the battery switch and the converter device. The converter device can be a current converter, such as a converter or an inverter.

[0019] An electric axle drive for a motor vehicle comprises an electric machine, a transmission and an embodiment of the converter device mentioned here. By using the converter device, the current required for the operation of the electric machine can be provided. By using the transmission device, the torque provided by the electric machine can be converted into a driving torque for driving at least one wheel of the motor vehicle. The transmission device can have a transmission mechanism for reducing the rotational speed of the electric machine and an optional differential.

[0020] Accordingly, a motor vehicle can comprise the aforementioned converter device and, in addition or as an alternative, the aforementioned electric axle drive.

[0021] A method for monitoring a closed state is provided for a battery switch. The battery switch has a first switch terminal for connecting the battery switch to an electrode of a battery and a second switch terminal for connecting the battery switch to an electrode of an intermediate circuit. The method is implemented by using a series circuit with an energy source and a diode and by using an evaluation circuit. In this case, the series circuit is connected in parallel with the battery switch. The energy source has a first energy source terminal and a second energy source terminal. The diode has a first diode terminal and a second diode terminal, wherein the first diode terminal is connected to the second energy source terminal. The method comprises a generation step and a provision step. In the generation step, a current flow or a voltage is generated between the first switch terminal of the battery switch and the second switch terminal of the battery switch. The generation step is implemented by using the energy source. In the provision step, an evaluation signal indicating the closed state of the battery switch is provided. The provision step is implemented by using the evaluation circuit and the potential present at the first diode terminal. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention is explained in detail by way of example in conjunction with the accompanying drawings.

[0023] Figure 1 A circuit diagram of an embodiment of a monitoring device is shown;

[0024] Figure 2 A circuit diagram of an embodiment of a monitoring device is shown;

[0025] Figure 3 A circuit diagram of an embodiment of a monitoring device is shown;

[0026] Figure 4 A circuit diagram of an embodiment of a monitoring device is shown;

[0027] Figure 5 A schematic diagram of an embodiment of a motor vehicle is shown; and

[0028] Figure 6 A flow chart diagram of one embodiment of a method for monitoring a closed state of a battery switch is shown.

[0029] In the following description of preferred embodiments of the present invention, the same or similar reference numerals are used for elements shown in the various figures and having similar functions, wherein repeated description of these elements is omitted. DETAILED DESCRIPTION

[0030] Figure 11 shows a circuit diagram of an embodiment of a monitoring device 100. The monitoring device 100 is designed to monitor the closed state of a battery switch 105. According to the embodiment shown, the battery switch 105 is used to connect or disconnect a battery 110 from an intermediate circuit 120. A first switch terminal 106 of the battery switch 105 is connected to a first electrode 102 of the battery 110, and a second switch terminal 108 of the battery switch 105 is connected to a first electrode 104 of the intermediate circuit 120.

[0031] Monitoring device 100 is connected only by way of example and is shown as a component of converter device 175. Converter device 175 has converter device 185 for converting or transforming a battery voltage of battery 110 or an intermediate circuit voltage of intermediate circuit 120 into a drive voltage which can be used, for example, for operating an electric machine.

[0032] According to one embodiment, the battery 110 is used as the primary energy storage in a battery-operated drive train of a vehicle. The energy stored in the battery 110 is appropriately converted by the converter device 175 and then delivered to the electric machine, for example, see Figure 5 . The converter device 175 requires an intermediate storage for this purpose, which is implemented as an intermediate circuit 120. The power supply line from the battery 110 to the intermediate circuit 120 is disconnected via a mechanical or electrical switch (here, the battery switch 105), so that although the battery 110 is charged, no voltage can be established at the converter device 185. In the event of a fault, the battery 110 is disconnected from the rest of the system, and the voltage at the intermediate circuit 120 is discharged via discharge. For safety reasons, there are two discharge paths here. One is passive discharge as an ohmic voltage divider, which is applied between the positive and negative poles of the intermediate circuit. In order to keep the loss energy during passive discharge low, a long time, for example 6 minutes, is required until the voltage at the intermediate circuit capacitor is sufficiently discharged after the battery 110 is disconnected, typically below 60 volts. The second measure is active discharge. This active discharge can be turned on as needed, so that the intermediate circuit 120 can be sufficiently discharged in a short time, for example within two seconds, after the battery 110 is disconnected. Due to the otherwise very high power loss, this path is not used permanently, but is only opened as soon as battery 110 is safely disconnected.

[0033] If a state now occurs in which the battery switch 105 of the battery 110 is not reliably disconnected, ie the battery 110 is still connected to the intermediate circuit 120 despite the disconnection command, active discharging is not performed or must be stopped again within a short time.

[0034] To safely detect the closed state of the battery switch 105 , the monitoring device 100 has a series circuit 135 consisting of a diode 130 and an energy source 140 and also an evaluation circuit 150 . The series circuit 135 consisting of a diode 130 and an energy source 140 is connected in parallel with the battery switch 105 .

[0035] According to various exemplary embodiments, the monitoring device 100 comprises only the series circuit 135 and the evaluation circuit 150 or additionally also the battery switch 105 .

[0036] The energy source 140 has a first energy source terminal 142 and a second energy source terminal 144. For example, the energy source 140 is configured as a current source in order to generate a current flow between the first switch terminal 106 of the battery switch 105 and the second switch terminal 108 of the battery switch 105. For this purpose, the first energy source terminal 142 is connected to the second switch terminal 108, for example. The ground potential terminal 160 is connected between the first energy source terminal 142 and the second switch terminal 108 only by way of example.

[0037] The diode 130 has a first diode terminal 132 and a second diode terminal 134. In this case, the first diode terminal 132 is, for example, an anode, and the second diode terminal 134 is a cathode. The first diode terminal 132 is connected to the second energy source terminal 144, and the second diode terminal 134 is, for example, connected to the first switch terminal 106. The diode 130 is therefore connected in the reverse direction in the direction of the first switch terminal 106.

[0038] The evaluation circuit 150 is configured to provide an evaluation signal 195 by using the potential present at the interception point. The evaluation signal 195 indicates the closed state of the battery switch 105. Exemplarily, the interception point is located on the connecting line connecting the first diode terminal 132 to the second energy source terminal 144. Therefore, the voltage signal for generating the evaluation signal 195 corresponds not only to the potential present at the first diode terminal 132, but also to the potential present at the second energy source terminal 144. The evaluation circuit 150 has a suitable circuit for generating the evaluation signal 195 depending on the magnitude of the potential.

[0039] According to one embodiment, the evaluation circuit 150 comprises a comparator 158. The comparator 158 has a first input 152, a second input 154 and an output 156. In this case, the comparator 158 is connected to the first diode terminal 132, for example, via the first input 152. The comparator 158 is connected to the reference voltage terminal 180, for example, via the second input 154. The comparator 158 is configured to provide an evaluation signal 195 at the output 156 by using the potential present at the first input 152 and the reference potential of the reference voltage terminal 180. According to one embodiment, the comparator 158 is connected to ground.

[0040] According to one exemplary embodiment, first electrode 102 of battery 110 and first electrode 104 of intermediate circuit 120 are each designed as a positive pole.

[0041] When battery switch 105 is closed, current flows from energy source 140 in flow direction 190 to first switch terminal 106 and via battery switch 105 to second switch terminal 108. In this closed state of battery switch 105, battery 110 is coupled to intermediate circuit 120.

[0042] The intermediate circuit 120 can be discharged quickly, for example, by means of active discharge. Active discharge is only carried out when the battery 110 is disconnected from the intermediate circuit 120. For this purpose, the battery switch 105 is opened, thereby preventing the current from flowing through the battery switch 105. The diode 130 blocks the current flow in the blocking direction. Instead, the voltage of the energy source 140 is applied. This voltage is detected by the evaluation circuit 150 (for example, the comparator 158) and used to provide the evaluation signal 195. The evaluation signal 195 indicates, for example, via a first signal state that the battery 110 is disconnected. Thus, for example, an active discharge of the intermediate circuit 120 can be carried out.

[0043] The concept presented here introduces a measure that checks the disconnection of battery 110 from intermediate circuit 120 before starting active discharging. This check can exclude the start of active discharging when battery 110 is connected. This can avoid high energy losses and allow the dimensioning of circuit elements to be carried out in a completely function-oriented manner.

[0044] The approach presented here is based on the concept of a continuity check. According to one embodiment, desaturation detection is usually included in the gate driver of the power electronics for detecting short circuits. The method used in desaturation detection is applied to the continuity check. For this purpose, a monitoring device 100, which can also be referred to as a circuit, is arranged at the terminals 106, 108 of a battery switch 105 for disconnecting a battery 110.

[0045] According to one embodiment, Figure 1A monitoring device 100 for detecting disconnection of an intermediate circuit 120 is shown. If the battery switch 105 is closed, the current of the energy source 104 (which can also be referred to as iDESAT) can flow through the diode 130 and the battery switch 105, and no voltage is built up. If the switch is open, the diode 130 blocks the reverse voltage of the battery 110 and does not cause the iDESAT current to flow. At the output of the energy source 104, the maximum available voltage of the energy source 104 appears, which is detected via the comparator 158. An evaluation signal 195, which can also be referred to as vID, indicates whether the battery 110 is disconnected. If an instruction to disconnect the battery 110 is given, and the switch cannot be disconnected due to a fault, this situation is detected and active discharge is not activated.

[0046] Figure 2 FIG. 1 is a circuit diagram of an embodiment of the monitoring device 100. The monitoring device 100 and Figure 1 106 , but adapted to the case where the battery switch 105 is arranged between the second electrode 202 of the battery 110 and the second electrode 204 of the intermediate circuit 120 , wherein the second electrodes 202 , 204 are each designed as negative poles. Thus, the first energy source terminal 142 of the energy source 140 is connected to the first switch terminal 106 , and the second diode terminal 134 of the diode 130 is connected to the second switch terminal 108 .

[0047] Evaluation circuit 150 according to Figure 1 is designed in order to provide the evaluation signal 195 by using the potential present at the interception point between the first diode terminal 132 and the second energy source terminal 144 .

[0048] therefore, Figure 2 It is shown that when the battery switch 105 is in the negative connection state, Figure 1 How the monitoring equipment is adjusted is shown in .

[0049] exist Figure 1 In the embodiment of the present invention, the reference potential of the monitoring device is always the positive pole of the intermediate circuit 120; Figure 2 It is obtained that the negative pole of the battery 110 is the reference potential of the monitoring device 100 .

[0050] Figure 3 FIG. 1 is a circuit diagram of an embodiment of the monitoring device 100. The monitoring device 100 and Figure 1 The monitoring device 100 is similar to the monitoring device 100 , but differs in that the energy source 140 is designed as a voltage source.

[0051] The first electrode 102 of the battery 110 and the first electrode 104 of the intermediate circuit 120 are each designed as a positive pole.

[0052] According to one embodiment, the energy source 140 has a first resistor 300, a second resistor 305 and a supply potential 310 (which may also be referred to as Vcc). Here, the first resistor 300, which may also be referred to as R1, is connected, for example, between the supply potential 310 and the second energy source terminal 144 of the energy source 140. The second resistor, which may also be referred to as R2, is connected between the first energy source terminal 142 and the second energy source terminal 144 of the energy source 140. The first resistor 300 and the second resistor 305 are formed as a voltage divider.

[0053] In other words, Figure 3 In FIG. 1 , a voltage source with a high-ohmic voltage divider is also used instead of the current source iDESAT. If the battery switch 105 is closed, a voltage, which can also be referred to as Vcc, drops at the first resistor 300, and there is no voltage at the input 152 of the comparator 158. If the switch is open, a voltage divider is obtained consisting of the first resistor 300 and the second resistor 305, so that a voltage that can be set via the resistor divider is generated at the input 152 of the comparator 158.

[0054] Figure 4 FIG. 1 is a circuit diagram of an embodiment of the monitoring device 100. The monitoring device 100 and Figure 1 The monitoring device 100 is similar to the embodiment of the present invention, except that the series circuit 135 includes a third resistor 400 .

[0055] The first electrode 102 of the battery 110 and the first electrode 104 of the intermediate circuit 120 are each designed as a positive pole.

[0056] For example, the diode 130 is connected between the third resistor 400 and the energy source 140 .

[0057] As soon as the battery 110 is disconnected from the intermediate circuit 120, no recovery is performed or the energy input of the motor into the intermediate circuit is technically prevented, because otherwise the recovery energy generated by the rotation of the motor will overcharge the intermediate circuit 120. However, a slight overcharging of the intermediate circuit 120 compared to the battery 110 is also allowed. If the intermediate circuit voltage is expected to rise above the battery voltage during operation (which may also occur when the battery is not disconnected for recovery), the third resistor 400, which can also be called a high-ohmic resistor R3, is added. The current intensity of the current source iDESAT, the reference voltage of the reference voltage terminal 180, which can also be called uRef, and the resistance value R3 of the third resistor 400 are coordinated with each other to ensure safe operation of the monitoring device 100.

[0058] Combination Figures 1 to 4 The described embodiments can be combined respectively. For example, Figure 1 , Figure 2 and Figure 4 The current source iDESAT shown in FIG. 1 is replaced by a current source having Figure 3 The first resistor and the second resistor are connected to the voltage source Vcc and combined with Figure 2 The negative electrode between the middle battery 110 and the intermediate circuit 120 is connected.

[0059] Figure 5 A schematic diagram of an embodiment of a motor vehicle 500 is shown.

[0060] The motor vehicle 500 is provided with an electric axle drive 510 with an electric motor 505. The electric energy for operating the electric motor 505 is provided by an energy supply device (e.g., a battery 110). For example, direct current is provided by the battery 110, which is converted into alternating current, e.g., three-phase alternating current, by using an inverter device 175 and provided to the motor 505. The shaft driven by the motor 505 is coupled to at least one wheel 508 of the motor vehicle 500 directly or by using a transmission 506. Therefore, the motor vehicle 500 can move forward by using the motor 505. According to one embodiment, the electric axle drive 510 includes a housing in which the inverter device 175, the motor 505, and the transmission 506 are arranged integrally.

[0061] The converter device 175 includes a converter device 185 for converting a battery voltage into a drive voltage and a battery switch 105. Here, the battery switch 105 is connected to the converter device 185 via an intermediate circuit. The battery switch 105 connects the battery 110 to the intermediate circuit of the converter device 185.

[0062] Figure 6 A flow chart of an embodiment of a method 600 for monitoring a closed state of a battery switch is shown. The battery switch is, for example, the battery switch of the aforementioned figures. The method 600 comprises a generating step 605 and a providing step 610. In the generating step 605, a current flow or a voltage is generated between a first switch terminal and a second switch terminal of the battery switch. The generating step 605 is performed using an energy source.

[0063] In a providing step 610, an evaluation signal is provided which indicates a closed state of the battery switch. The providing step 610 is performed using the evaluation circuit and the potential present at the first diode terminal.

[0064] Reference numerals list

[0065] 100 Monitoring equipment

[0066] 102 First electrode of the battery

[0067] 104 First electrode of intermediate circuit

[0068] 105 Battery switch

[0069] 106 First switch terminal of battery switch

[0070] 108 Second switch terminal of battery switch

[0071] 110 Batteries

[0072] 120 Intermediate circuit

[0073] 130 diode

[0074] 132 First diode terminal

[0075] 134 Second diode terminal

[0076] 135 Series Circuit

[0077] 140 Energy Source

[0078] 142 First energy source terminal

[0079] 144 Second energy source terminal

[0080] 150 Evaluation Circuit

[0081] 152 First input

[0082] 154 Second input terminal

[0083] 156 Output

[0084] 158 Comparator

[0085] 160 Ground potential terminal

[0086] 175 Converter equipment

[0087] 180 Reference voltage terminal

[0088] 185 Converter device

[0089] 190 Flow direction

[0090] 195 Evaluation Signal

[0091] 202 Second electrode of battery

[0092] 204 Second electrode of intermediate circuit

[0093] 300 First resistor

[0094] 305 Second resistor

[0095] 310 Supply potential

[0096] 400 Third resistor

[0097] 500 Motor Vehicles

[0098] 505 Motor

[0099] 506 Transmission

[0100] 508 Wheels

[0101] 510 Tramway Axle Driver

[0102] 600 Method for monitoring the closed state of a battery switch

[0103] 605 Generation Steps

[0104] 610 Provide Steps

Claims

1. A monitoring device (100) for monitoring the closed state of a battery switch (105), wherein: The battery switch (105) has a first switch terminal (106) for connecting the battery switch (105) to an electrode (102; 202) of a battery (110) and a second switch terminal (108) for connecting the battery switch (105) to an electrode (104; 204) of an intermediate circuit (120), wherein the monitoring device (100) has the following features: A series circuit (135) having an energy source (140) and a diode (130), wherein the series circuit (135) is connected in parallel with the battery switch (105); The energy source (140) has a first energy source terminal (142) and a second energy source terminal (144), wherein the energy source (140) is configured to generate a current flow or a voltage between a first switch terminal (106) of the battery switch (105) and a second switch terminal (108) of the battery switch (105); The diode (130) has a first diode terminal (132) and a second diode terminal (134), wherein the first diode terminal (132) is connected to the second power supply terminal (144); and An evaluation circuit (150) is configured to provide an evaluation signal (195) indicating a closed state of the battery switch (105) by using a potential present at the first diode terminal (132).

2. The monitoring device (100) according to claim 1, wherein: The diode (130) has a cathode and an anode, wherein the first diode terminal (132) is the anode and the second diode terminal (134) is the cathode.

3. The monitoring device (100) according to any one of the preceding claims, wherein: The evaluation circuit (150) comprises a comparator (158), wherein the comparator (158) has a first input (152), a second input (154) and an output (156), wherein the comparator (158) is connected to the first diode terminal (132) via the first input (152) and to a reference voltage terminal (180) via the second input (154), wherein the comparator (158) provides the evaluation signal (195) at the output (156).

4. The monitoring device (100) according to any one of the preceding claims, wherein: The first energy source terminal (142) is connected to the second switch terminal (108), and wherein the second diode terminal (134) is connected to the first switch terminal (106).

5. The monitoring device (100) according to any one of claims 1 to 3, wherein: The first energy source terminal (142) is connected to the first switch terminal (106), and wherein the second diode terminal (134) is connected to the second switch terminal (108).

6. The monitoring device (100) according to any one of the preceding claims, wherein: The energy source (140) is designed as a current source.

7. The monitoring device (100) according to any one of claims 1 to 5, wherein: The energy source (140) is designed as a voltage source.

8. The monitoring device (100) according to any one of the preceding claims, wherein: The energy source (140) comprises a first resistor (300), a second resistor (305) and a supply potential (310), wherein the first resistor (300) is connected between the supply potential (310) and a second energy source terminal (144) of the energy source (140), and wherein the second resistor (305) is connected between the first energy source terminal (142) and the second energy source terminal (144) of the energy source (140).

9. The monitoring device (100) according to any one of the preceding claims, wherein: The series circuit (135) has a third resistor (400).

10. The monitoring device (100) according to claim 9, wherein: The diode (130) is connected between the third resistor (400) and the energy source (140).

11. The monitoring device (100) according to any of the preceding claims, comprising the battery switch (105) having a first switch terminal (106) for connecting the battery switch (105) to an electrode (102; 202) of the battery (110) and a second switch terminal (108) for connecting the battery switch (105) to an electrode (104; 204) of the intermediate circuit (120).

12. A converter device (175) having a monitoring device (100) according to claim 11, the converter device having an intermediate circuit (120) and a converter device (185) for converting a battery voltage into a drive voltage, wherein: The intermediate circuit (120) is connected between the battery switch (105) and the converter device (185).

13. An electric axle drive (510) for a motor vehicle (500), the electric axle drive having at least an electric motor (505), a transmission (506) and a converter device (175), characterized in that: The converter device (175) is designed according to claim 12.

14. A motor vehicle (500) comprising an electric vehicle axle drive (510) according to claim 13 and / or a converter device (175) according to claim 12.

15. A method (600) for monitoring the closed state of a battery switch (105), wherein: The battery switch (105) has a first switch terminal (106) for connecting the battery switch (105) to an electrode (102; 202) of a battery (110) and a second switch terminal (108) for connecting the battery switch (105) to an electrode (104; 204) of an intermediate circuit (120), wherein the method (600) is implemented by using a series circuit (135) having an energy source (140) and a diode (130) and by using an evaluation circuit (150), wherein the series circuit (135) is connected in parallel with the battery switch (105), wherein the energy source (140) has a first energy source terminal (142) and a second energy source terminal (144), wherein the diode (130) has a first diode terminal (132) and a second diode terminal (134), wherein the first diode terminal (132) is connected to the second energy source terminal (144), and wherein the method (600) comprises the following steps: generating (605) a current flow or a voltage between a first switch terminal (106) of the battery switch (105) and a second switch terminal (108) of the battery switch (105) by using the energy source (140); and By using the evaluation circuit (150) and the potential present at the first diode terminal (132), an evaluation signal (195) is provided (610) which indicates a closed state of the battery switch (105).

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