Driver circuit protection device and driver circuit protection method

Abstract

This invention relates to protection for a driver circuit used to operate a semiconductor switch. For this purpose, the voltage drop across the series resistor between the driver circuit and the control connection terminal of the semiconductor switch is evaluated. If the voltage drop across the series resistor exceeds a predetermined threshold and remains above that threshold for at least a predetermined duration, the driver circuit for the semiconductor switch is then deactivated.

Description

Technical Field

[0001] The present invention relates to a protection device for a driver circuit for controlling a semiconductor switch and a method for protecting a driver circuit for controlling a semiconductor switch. The present invention also relates to a control device for a semiconductor switch and an inverter device. Background Art

[0002] Electric drive systems, for example for fully or partially electrically driven vehicles, usually include an electric machine fed by a converter. The converter usually includes a plurality of half-bridges with power semiconductor switches. These power semiconductor switches are actuated via driver circuits, which amplify control signals in order to provide sufficient electrical power to actuate the power semiconductor switches.

[0003] Document DE 10 2015 217 175 A1 discloses a control circuit for an inverter of a vehicle. The inverter is designed to convert a DC voltage from an electrical energy storage device into an AC current, which is used to operate an electric motor of the vehicle. The control circuit includes a driver unit that generates inverter control signals for switching elements of the inverter.

[0004] If a power semiconductor switch is defective, a short circuit may occur between the control terminal of the power semiconductor switch and the other output of the power semiconductor switch. This short circuit may severely load the output of the driver stage for driving the power semiconductor switch. Summary of the invention

[0005] The invention discloses a protection device for a driver circuit for actuating a semiconductor switch and a method for protecting a driver circuit for actuating a semiconductor switch having the features of the independent claims. Further advantageous embodiments are the subject matter of the dependent claims.

[0006] According to this provision:

[0007] A protection device for a driver circuit for controlling a semiconductor switch. The driver circuit is electrically coupled to a control connection of the semiconductor switch by means of an electrical series resistor. The protection device is designed to detect a voltage drop across the series resistor of the driver circuit. The protection device is further designed to deactivate the driver circuit if a predetermined characteristic is detected in the detected voltage drop. In particular, the driver circuit can be deactivated if the detected voltage drop exceeds a predetermined value for at least a predetermined duration.

[0008] It also provides that:

[0009] A method for protecting a driver circuit for actuating a semiconductor switch, wherein the driver circuit is electrically coupled to a control connection of the semiconductor switch by means of an electrical series resistor. The method comprises the steps of detecting a voltage drop across the series resistor of the driver circuit and deactivating the driver circuit if a predetermined characteristic is detected in the detected voltage drop. In particular, the driver circuit can be deactivated if the detected voltage drop exceeds a predetermined threshold value for at least a predetermined duration.

[0010] Advantages of the present invention

[0011] The invention is based on the knowledge that in the event of a fault in a power semiconductor switch, in particular in the event of a short circuit, a short circuit may occur between the control terminal and the other terminals of the power semiconductor switch. In the event of such a short circuit, a very strong load may be exerted on the driver circuit that feeds the control input of the power semiconductor switch, that is, a relatively high current may flow. Such a strong load on the output of the driver circuit may possibly lead to further damage in the driver stage or other components. As a result, there is the risk that a fault in the power semiconductor switch may lead to further damage to the driver circuit.

[0012] Therefore, one idea of ​​the present invention is to take this knowledge into account and to provide a protection for the driver circuit of the semiconductor switch, which protection enables the driver stage of the semiconductor switch with the fault to be shut down reliably in the event of a fault. In this way, further damage within the driver stage can be prevented. In addition, by shutting down the driver stage of the faulty semiconductor switch as soon as possible, it is also possible to avoid the fault from propagating to other components, such as other driver stages, etc.

[0013] If a faulty power semiconductor switch is detected early and the driver stage involved is then disabled for this semiconductor switch, the fault can be prevented from propagating to other components if necessary. This makes it possible, for example, to switch the electrical system to a safe operating state in the event of a fault, such as an active short circuit, etc. In this way, the safety of the electric drive system can be increased.

[0014] Furthermore, by deactivating the driver circuit in the event of a fault in a connected semiconductor switch, damage to other components can be prevented. The number of damaged components can thus be reduced in the event of a fault. This allows for rapid and cost-effective repairs.

[0015] According to one embodiment, the protection device comprises a low-pass filter. The low-pass filter is designed to filter the detected voltage drop across the series resistor. In particular, the low-pass filter can be designed to filter high-frequency components in the detected voltage drop. The switching processes that are common during the operation of the semiconductor switch usually result in short, high-frequency switching pulses. These switching pulses can be eliminated or at least minimized by appropriate low-pass filtering, so that the voltage drop across the series resistor caused by the common switching pulses during operation has no significant influence on the signal to be evaluated.

[0016] According to one embodiment, the protection device comprises a comparison device. The comparison device is designed to compare the value of the voltage drop detected across the series resistor with a predetermined threshold value. If the detected voltage drop across the series resistor, in particular the smoothed or low-pass filtered voltage drop across the series resistor, exceeds the predetermined threshold value, this may mean that the output of the driver circuit of the semiconductor switch is strongly loaded for a longer period of time. This usually only occurs in the event of a fault.

[0017] According to one embodiment, the predetermined threshold value of the comparison device can be adapted. In particular, the predetermined threshold value of the comparison device can be adapted as a function of the supply voltage of the driver circuit. If more than one voltage is supplied to the driver circuit, the threshold value can be adapted as a function of at least one of the multiple supply voltages. By adapting the threshold value for detecting fault situations, fluctuations in framework conditions, such as fluctuating supply voltages and the like, can also be taken into account. Thus, for example, fluctuations in the supply voltage of the driver circuit can also lead to a higher or lower voltage drop across the series resistor even in normal, fault-free operation. Such effects can be taken into account and compensated by suitable adaptation of the detection threshold value.

[0018] According to one embodiment, the protection device comprises a storage device. The storage device is designed to switch from a first state to a second state if the comparison device detects that the voltage drop exceeds a predetermined threshold value. In particular, the storage device can also remain in the second state when the voltage drop across the series resistor is again below the predetermined threshold value. In this way, it can be ensured that the driver circuit is permanently turned off after a fault is detected. For example, the storage device can be a bistable multivibrator, such as a trigger or the like. If necessary, the storage device can be reset by applying a suitable reset signal, that is, switched to the first state. If the storage device is in the first state, the driver circuit for controlling the semiconductor switch can be activated.

[0019] Furthermore, a control device for a semiconductor switch is provided, which has a driver circuit and a protective device according to the invention. The driver circuit is designed to provide a control signal at a control input of the semiconductor switch.

[0020] Furthermore, an inverter arrangement having a plurality of semiconductor switches and the above-described control device is provided, wherein each driver circuit is designed to actuate at least one of the plurality of semiconductor switches.

[0021] According to one embodiment of the inverter device, a separate control device is provided for each semiconductor switch of the plurality of semiconductor switches.

[0022] As long as it makes sense, the above designs and extensions can be combined with each other at will. Other designs, extensions and implementations of the present invention also include combinations that are not explicitly mentioned of the features of the present invention described above or below with respect to the embodiments. In particular, those skilled in the art will also add various aspects as improvements or supplements to the corresponding basic forms of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Other features and advantages of the present invention are explained below based on the accompanying drawings.

[0024] Figure 1 A schematic diagram of a control device for a semiconductor switch having a protection device according to one embodiment is shown;

[0025] Figure 2 shows a schematic diagram of a control device for a semiconductor switch having a protection device according to another embodiment;

[0026] Figure 3 A schematic diagram showing an inverter device according to an embodiment; and

[0027] Figure 4 A flow chart based on a method for protecting a driver circuit according to one embodiment is shown. DETAILED DESCRIPTION

[0028] Figure 1 A schematic diagram of a block diagram of a control device for controlling a semiconductor switch 3 according to one embodiment is shown. The control device for controlling the semiconductor switch 3 includes a driver circuit 2 and a protection device 1 for the driver circuit 2. A control signal can be provided at an input terminal E of the driver circuit 2, which is prepared by the driver circuit 2 so as to provide a control signal with sufficient voltage magnitude and power to drive the control connection terminal of the semiconductor switch 3 at an output terminal A of the driver circuit 2. To this end, the input signal of the driver circuit 2 can be received and prepared by a circuit 23 (e.g., a gate driver IC, etc.). The signal can then be amplified by an amplifier circuit 22 and provided at an output terminal A via a series resistor 21. The output terminal A of the driver circuit 2 is electrically coupled to the control connection terminal of the semiconductor switch 3, so that the signal provided at the output terminal A can control the semiconductor switch 3.

[0029] During the actuation of the semiconductor switch 3 , a current flows from the output A of the driver circuit 2 to the control connection of the semiconductor switch 3 during a relatively short period of time.

[0030] If a fault situation occurs in the semiconductor switch 3, a short circuit may also occur between the control terminal of the semiconductor switch 3 and the other terminals of the semiconductor switch 3. This short circuit may result in a greater current being able to flow from the output A of the driver circuit 2 in the direction of the semiconductor switch 3 for a longer period of time. Such a high current also results in a corresponding voltage drop across the series resistor 21.

[0031] The protection device 1 for the driver circuit 2 is coupled to the driver circuit 2 so that the protection device 1 can detect the voltage drop across the series resistor 21. A normal switching process for the control connection of the semiconductor switch 3 only results in a relatively short current pulse and thus a short voltage drop across the series resistor 21, while a fault in the semiconductor switch 3 results in a longer current and thus also in a voltage drop across the series resistor 21 that lasts for a longer time. Such a voltage drop that lasts longer than a predetermined time can be detected by the protection device 1. The protection device 1 can then deactivate the driver circuit 2. For example, the protection device 1 can provide a control signal on the driver circuit 2, which activates or deactivates the driver circuit 2. For example, the driver circuit 2 can only be activated if the protection device 1 sends an active release signal. If the active release signal is turned off, the driver circuit 2 is then also deactivated. Of course, the reverse is also possible, that is, the protection device 1 outputs an active signal to deactivate the driver circuit 2.

[0032] As described above, during normal operation, a normal control pulse for actuating the semiconductor switch 2 only causes a relatively brief voltage drop across the series resistor 21. In contrast, in the event of a fault, the voltage drop across the series resistor 21 can be detected over a longer period of time. In order to distinguish between these two states, a low-pass filter 11 can be provided for the driver circuit 2 in the protection device 1, which filters the signal corresponding to the voltage drop across the series resistor 21. In this way, high-frequency signal components can be eliminated or at least minimized, so that only low-frequency components of the voltage drop across the series resistor 21 are evaluated for further evaluation. Any low-pass filter can be used for the low-pass filtering, such as an RC element or the like.

[0033] The correspondingly prepared signal can then be supplied to a comparator 12 which compares the detected voltage drop across the series resistor 21 with a predetermined threshold value. If the detected voltage drop across the series resistor 21 exceeds the predetermined threshold value, this can be evaluated as an indication of a fault in the semiconductor switch 3.

[0034] If necessary, the predetermined threshold value used by the comparison device 12 to compare the voltage drop across the series resistor 21 can be adapted. For example, the threshold value used for the comparison can be adapted as a function of the supply voltage of the driver circuit 2. Changes in the supply voltage of the driver circuit 2 can, under certain circumstances, lead to a change in the current from the driver circuit 2 to the control connection of the semiconductor switch 3, also as a function of the magnitude of the supply voltage. By (dynamically) adapting the detection threshold value in the comparison device 12, this effect can be taken into account and, if necessary, compensated.

[0035] The output of the comparison device 12 can be coupled to the storage device 13. When the comparison device 12 detects that the voltage drop across the series resistor 21 exceeds the predetermined threshold value, the storage device 13 can, for example, switch from the first state to the second state. In addition, even if the voltage drop across the series resistor 21 drops below the predetermined threshold value again, the storage device 13 can remain in the second state. In this way, after a fault is detected, that is, after the voltage drop across the series resistor 21 exceeds the predetermined duration, the storage device 13 can detect the fault and provide a shutdown signal for deactivating the driver circuit 2. The shutdown signal should be permanently maintained after the fault is detected. For example, a trigger or the like can be used for this purpose. If necessary, the storage device 13 can be reset with the help of a reset signal (reset).

[0036] Figure 2 FIG. 1 is a schematic diagram of a block diagram of a control device for a semiconductor switch 3 according to another embodiment. Figure 2 The control device of differs from the above-described control devices in particular in that the driver IC 23 of the driver circuit 2 divides the control signal into two signals. The corresponding signal paths are characterized by the letters a and b. In order to close the semiconductor switch 3, the upper path a can, for example, conduct a positive output current. In this case, path b is then high-ohmic. In order to open the semiconductor switch 3, the lower path b can conduct a negative output current. In this case, path a is then high-ohmic. In this way, separate control signals for opening and closing the semiconductor switch 3 are generated. In addition, the control device for operating the semiconductor switch 3 and in particular the protection device 1 correspond to the control device according to Figure 1 The above implementation method.

[0037] Figure 3A schematic diagram of an inverter device according to one embodiment is shown. The inverter device may include, for example, three half-bridges, each of which has two semiconductor switches 3. Each of these semiconductor switches 3 can be controlled by a driver circuit 2. In addition, a protection device 1 according to one of the above embodiments can be provided for each driver circuit 2. In this way, a separate protection can be provided for the driver circuit 2 of the semiconductor switch 3. In particular, if a fault occurs in one of the semiconductor switches 3, in particular a short circuit occurs between the control connection terminal and the other connection terminals, the corresponding driver circuit 2 can be deactivated by the corresponding protection device 1. In this case, the operation of the remaining semiconductor switches and the associated driver circuit 2 is not affected. In particular, if the inverter circuit is provided, for example, for controlling a motor, the inverter device can be switched to a safe operating state in the event of a fault in one of the semiconductor switches 3.

[0038] Such a safe operating state can be, for example, an active short circuit, in which all upper or lower semiconductor switches are closed simultaneously. For example, if a fault occurs in one of the lower semiconductor switches 3 and a short circuit associated therewith occurs in the corresponding semiconductor switch 3, the other two lower semiconductor switches can also be closed. The three upper semiconductor switches 3 are all open here. A similar process can also take place in the event of a short circuit in one of the upper semiconductor switches 3. In this case, by deactivating the driver circuit of the faulty semiconductor switch 3, the remaining semiconductor switches 3 can continue to be safely actuated.

[0039] Figure 4 A schematic diagram of a flow chart based on a method for protecting a driver circuit for controlling a semiconductor switch according to an embodiment is shown. The method can be applied in particular to a driver circuit 2 for controlling a semiconductor switch 3, wherein the driver circuit 2 is electrically coupled to a control connection of the semiconductor switch 3 by means of an electrical series resistor 21. In step S1, a voltage drop across the series resistor 21 of the driver circuit 2 is detected. In step S2, the driver circuit 2 is deactivated when a predetermined feature is detected in the detected voltage drop. As described above, the predetermined feature can be, for example, that the voltage drop exceeds a threshold value during a predetermined time period. For this purpose, as described above, the voltage drop can be filtered by means of a low-pass filter and the filtered voltage drop can be compared with a threshold value. If the detected voltage drop exceeds a predetermined threshold value, and if the threshold value is exceeded for at least a predetermined duration, the control of the semiconductor switch can be stopped. This stop can also be maintained when the detected voltage drop falls below the predetermined threshold value again.

[0040] In summary, the invention relates to the protection of a driver circuit for actuating a semiconductor switch. For this purpose, the voltage drop in a series resistor between the driver circuit and the control terminal of the semiconductor switch is evaluated. If the voltage drop across the series resistor exceeds a predetermined threshold value and exceeds the threshold value for at least a predetermined duration, the driver circuit for the semiconductor switch is then deactivated.

Claims

1. An inverter device, comprising: a plurality of semiconductor switches (3-i), and A plurality of control devices, wherein each control device is designed to actuate at least one semiconductor switch of the plurality of semiconductor switches (3-i) and each control device comprises: a driver circuit (2-i) designed to provide a control signal at a control input of the at least one semiconductor switch (3-i), and A protection device (1-i) for the driver circuit (2-i), wherein the driver circuit (2-i) is electrically coupled to a control connection of the semiconductor switch (3-i) by means of an electrical series resistor (21), wherein the protection device (1-i) is designed to detect a voltage drop across the series resistor (21) of the driver circuit (2-i) and to deactivate the driver circuit (2-i) if a predetermined characteristic is detected in the detected voltage drop, wherein the predetermined characteristic is designed so that the detected voltage drop exceeds a predetermined threshold value for at least a predetermined duration.

2. The inverter arrangement according to claim 1, wherein the protection device (1-i) has a low-pass filter (11), and the low-pass filter (11) is designed to filter the detected voltage drop across the series resistor (21).

3. The inverter device according to claim 1 or 2, wherein the protection device (1-i) has a comparison device (12), which is designed to compare the value of the detected voltage drop across the series resistor (21) with the predetermined threshold value. The inverter device according to claim 3 , wherein the predetermined threshold value is adaptable.

5. The inverter arrangement according to claim 4, wherein the predetermined threshold value is adaptable as a function of at least one supply voltage of the driver circuit (2-i).

6. The inverter device according to claim 3, wherein the protection device (1-i) has a storage device (13), and the storage device (13) is designed to switch from the first state to the second state if the comparison device (12) detects that the voltage drop exceeds the predetermined threshold value.

7. The inverter device according to claim 1, wherein a separate control device is provided for each semiconductor switch (3-i) of the plurality of semiconductor switches (3-i).

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