EP3949123A1

EP3949123A1 - Protection apparatus for a driver circuit, and method for protecting a driver circuit

Info

Publication number: EP3949123A1
Application number: EP20712533.7A
Authority: EP
Inventors: Tim Bruckhaus
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2019-03-29
Filing date: 2020-03-18
Publication date: 2022-02-09
Also published as: CN113597740A; WO2020200780A1; US20220360070A1; DE102019204429A1

Abstract

The present invention relates to the protection of a driver circuit for actuating a semiconductor switch. A voltage drop in a series resistor between the driver circuit and a control connection of the semiconductor switch is evaluated for this purpose. If the voltage drop across the series resistor exceeds a prespecified threshold value and this threshold value is exceeded for at least a predetermined period of time, the driver circuit for the semiconductor switch is then deactivated.

Description

description

title

Protection device for a driver circuit and method for protecting a

Driver circuit

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 arrangement.

State of the art

Electric drive systems, such as are used, for example, in fully or partially electrically driven vehicles, generally comprise an electric machine that is fed by a power converter. The converter usually includes several half bridges

Power semiconductor switches. These power semiconductor switches are controlled via a driver circuit which amplifies the control signals in order to provide sufficient electrical power for controlling the power semiconductor switches.

The 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 store into a

Convert alternating current with which an electrical machine of a vehicle is operated. The control circuit comprises a driver unit which generates inverter control signals for the switching elements of the inverter. In the event of a defect in a power semiconductor switch, a short circuit can occur between the control connection of the power semiconductor switch and a further output of the power semiconductor switch. Such a short circuit can damage an output of a driver stage for the

Driving the power semiconductor switch are heavily loaded.

Disclosure of the invention

The present invention discloses a protection device for a

Driver circuit for controlling a semiconductor switch, as well as a method for protecting a driver circuit for controlling a semiconductor switch with the features of the independent claims. More beneficial

Embodiments are the subject of the dependent claims.

Accordingly, it is provided:

A protection device for a driver circuit for controlling a

Semiconductor switch. The driver circuit is by means of an electrical

Series resistor electrically coupled to a control terminal of the semiconductor switch. The protective device is designed to detect a voltage drop across the series resistor of the driver circuit. The protection device is also designed to deactivate the driver circuit when a predetermined characteristic has been detected in the detected voltage drop. In particular, the driver circuit can be deactivated when the detected voltage drop exceeds a predetermined value for at least a predetermined period of time.

It is also planned:

A method for protecting a driver circuit for controlling a

Semiconductor switch, the driver circuit by means of an electrical

Series resistor is electrically coupled to the control terminal of the semiconductor switch. The method includes a step of detecting a

Voltage drop across the series resistor of the driver circuit, and a step for deactivating the driver circuits, if in the detected Voltage drop a predetermined characteristic has been detected.

In particular, the driver circuit is deactivated when the detected voltage drop exceeds a predetermined threshold value for at least a predetermined period of time.

Advantages of the invention

The present invention is based on the knowledge that in the event of a fault, in particular in the case of a breakdown, a

Power semiconductor switch to a short circuit between the

Control connection and another connection of the power semiconductor switch can come. In the event of such a short circuit, a driver circuit which feeds the control input of the power semiconductor switch can be very heavily loaded, that is, a relatively high electrical current can flow. This heavy load on the output of the driver circuit can possibly lead to further damage within the driver stage or also further components. As a result, there is the risk that a fault in a power semiconductor switch will lead to further damage to the driver circuit.

It is therefore an idea of the present invention to take this knowledge into account and to provide protection for a driver circuit of a semiconductor switch which, in the event of a fault, enables the driver stage with the defective semiconductor switch to be switched off reliably. In this way it is possible to prevent further damage within the driver stage. In addition, by switching off the driver stage of a defective semiconductor switch as soon as possible, it is also possible to prevent the fault from spreading into other components, for example into further driver stages or the like.

If a defective power semiconductor switch is detected early and the affected driver stage is then deactivated for this semiconductor switch, it may be possible to prevent the error from spreading to other components. This enables, for example, an electrical system in the event of a fault in a safe operating state, for example an active one Short circuit or the like. In this way, the safety of an electric drive system can be increased.

In addition, by deactivating the driver circuit in the event of a fault in the connected semiconductor switch, damage to further components can be prevented. In this way, the number of damaged components can be reduced in the event of a fault. This enables quick and inexpensive repairs.

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 higher-frequency components in the detected voltage drop. The usual switching operations during control of the

Semiconductor switches usually lead to short, higher frequency

Switching pulses. With a suitable low-pass filtering these

Switching pulses are eliminated or at least minimized so that the

Voltage drops across the series resistor due to the usual switching pulses during operation have no significant influence on the signal to be evaluated.

According to one embodiment, the protective device comprises a

Comparison facility. The comparison device is designed to compare a value of the detected voltage drop 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 a predetermined threshold value, this can be interpreted as an indication that the output of the driver circuit for the semiconductor switch is heavily loaded over a longer period of time. This usually only occurs in the event of an error.

According to one embodiment, the predetermined threshold value is

Adaptable comparison facility. In particular, the predetermined

Threshold value of the comparison device as a function of a

Supply voltage of the driver circuit can be adjusted. Will the Driver circuit provides more than one voltage, so the

Threshold value as a function of at least one of the several

Supply voltages can be adjusted. By customizing the

Threshold values for the detection of a fault can also fluctuate in the framework conditions, such as a fluctuating one

Supply voltage or the like. For example, fluctuations in the supply voltage of the

Driver circuit lead to higher or lower voltage drops occurring across the series resistor even in normal, error-free operation.

Such effects can be taken into account and compensated for by suitable adaptation of the detection thresholds.

According to one embodiment, the protective device comprises a

Storage facility. The memory device is designed to transition from a first state to a second state when the

Comparison device has detected that the voltage drop has exceeded the predetermined threshold value. In particular, the

Storage device retain the second state even if the voltage drop across the series resistor falls below the predetermined threshold value again. In this way, a permanent shutdown of the driver circuit after the detection of an error can be guaranteed.

For example, the memory device can be a bistable multivibrator, such as a flip-flop or the like.

If necessary, the memory device can be reset by applying a suitable reset signal, that is to say transferred to the first state. When the memory device is in the first state, the driver circuit can be activated for driving the semiconductor switch.

Furthermore, a control device for a semiconductor switch with a driver circuit and a protective device according to the invention is provided. The driver circuit is designed to be connected to a control input of the

Semiconductor switch to provide a control signal.

Furthermore, an inverter arrangement with a plurality of semiconductor switches and a control device described above is provided, each Driver circuit is designed to at least one of the plurality

To control semiconductor switches.

According to one embodiment of the inverter arrangement, there is a separate one for each semiconductor switch of the plurality of semiconductor switches

Control device provided.

The above configurations and developments can be combined with one another as desired, as far as this makes sense. Further refinements, developments and implementations of the invention also include combinations not explicitly mentioned above or below with regard to the

Embodiments described features of the invention. In particular, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic forms of the invention.

Brief description of the drawings

Further features and advantages of the present invention are explained below with reference to the figures. Show:

Figure 1: a schematic representation of a control device for a

Semiconductor switch with a protection device according to one embodiment;

Figure 2: a schematic representation of a control device for a

Semiconductor switch with a protective device according to a further embodiment;

FIG. 3: a schematic representation of an inverter arrangement according to an embodiment; and

Figure 4: a flow chart of how a method for protecting a

Driver circuit according to one embodiment is based.

Embodiments of the invention Figure 1 shows a schematic representation of a block diagram of a

Control device for controlling a semiconductor switch 3 according to one embodiment. The control device for controlling the semiconductor switch 3 comprises a driver circuit 2 and a protection device 1 for the

Driver circuit 2. At an input E of the driver circuit 2, a

Control signal are provided, which is processed by the driver circuit 2 in order to provide a control signal at the output A of the driver circuit 2 which has a sufficient voltage level and power to drive a control terminal of the semiconductor switch 3. For this purpose, the input signal of the driver circuit 2 can be received and processed by a circuit 23, for example a gate driver IC or the like. The signal can then be amplified by an amplifier circuit 22 and provided at output A via a series resistor 21. The output A of the driver circuit 2 is electrically coupled to the control connection of the semiconductor switch 3, so that the signal provided at the output A can control the semiconductor switch 3.

While the semiconductor switch 3 is being driven, a current flows from the output A of the driver circuit 2 to the control terminal of the semiconductor switch 3 for a relatively short period of time.

If a fault occurs in the semiconductor switch 3, a short circuit can also occur between the control connection of the semiconductor switch 3 and a further connection of the semiconductor switch 3. This short circuit can lead to the fact that a larger current can flow from the output connection A of the driver circuit 2 in the direction of the semiconductor switch 3 for a longer period of time. This high current flow also leads to a corresponding voltage drop across the series resistor 21.

The protective device 1 for the driver circuit 2 is coupled to the driver circuit 2 in such a way that the protective device 1 can detect a voltage drop across the series resistor 21. During normal switching processes for the control connection of the semiconductor switch 3 only to relatively short current pulses and the associated short voltage drops across the series resistor 21 lead, a fault in the semiconductor switch 3 leads to a longer current flow and, associated therewith, also to a voltage drop across the series resistor 21, which lasts for a longer time. Such a voltage drop, which lasts longer than a predetermined period of time, can be detected by the protective device 1. The protective device 1 can then deactivate the driver circuit 2. For example, the protective device 1 on the

Driver circuit 2 provide a control signal which activates or deactivates driver circuit 2. For example, the driver circuit 2 can only be activated as long as an active release signal is present from the protective device 1. If this active release signal is switched off, the driver circuit 2 is then also deactivated. Conversely, it is of course also possible for the protective device 1 to output an active signal for deactivating the driver circuit 2.

As already explained above, the normal control pulses for driving the semiconductor switch 2 cause only relatively brief voltage drops across the series resistor 21 during normal operation. In the event of a fault, however, a voltage drop across the series resistor 21 can be detected for a longer period of time. In order to distinguish between these two states, a low-pass filter 11 can be provided in the protective device 1 for the driver circuit 2, which filters a signal corresponding to the voltage drop across the series resistor 21. In this way, higher-frequency signal components can be eliminated or at least minimized, so that only the low-frequency component of the voltage drop across the series resistor 21 is evaluated for further evaluation. Any desired low-pass filter, for example an R-C element or the like, can be used for the low-pass filtering.

The correspondingly processed signal can then be fed to a comparison device 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 interpreted as an indication that an error has occurred in the semiconductor switch 3. If necessary, the specified threshold value with which the

Comparison device 12 compares the voltage drop across the series resistor 21. For example, the threshold for the

Comparison can be adapted as a function of a supply voltage of the driver circuit 2. A variation in the supply voltage of the

Driver circuit 2 can under certain circumstances also lead to the

Electric currents from the driver circuit 2 to the control terminal of the semiconductor switch 3 vary depending on the level of

Change supply voltage. Such effects can be taken into account and, if necessary, compensated for by a (dynamic) adaptation of the detection threshold in the comparison device 12.

An output of the comparison device 12 can be coupled to a storage device 13. The storage device 13 can, for example, change from a first state to a second state when the

Comparison device 12 detects that the voltage drop across the series resistor 21 exceeds the predetermined threshold value. In addition, the memory device 13 can also remain in the second state, even if the voltage drop across the series resistor 21 falls again below the predetermined threshold value. In this way, the

After a fault has been detected, that is, the voltage drop across the series resistor 21 has been exceeded for a predefined period of time, the memory device 13 detects a fault and provides a switch-off signal for deactivating the driver circuit 2. This switch-off signal should be maintained permanently after an error has been detected.

For example, a flip-flop or the like can be used for this purpose.

If necessary, the memory device 13 can be reset by means of a reset signal (reset).

Figure 2 shows a schematic representation of a block diagram of a

Control device for a semiconductor switch 3 according to another

Embodiment. The control device according to FIG. 2 differs from the control device described above in particular in that the driver IC 23 of the driver circuit 2 splits the control signal into two signals. The corresponding signal paths are indicated by the letters a and b marked. For closing the semiconductor switch 3, the upper path a can, for example, carry a positive output current. In this case, the path b is then high-resistance. To open the semiconductor switch 3, the lower path b can carry a negative output current. In this case, the path a is then high-resistance. In this way, separate control signals for opening and closing the semiconductor switch 3 are generated. In addition, the control device for controlling the semiconductor switch 3, and in particular the protective device 1, corresponds to the previously described embodiment according to FIG.

FIG. 3 shows a schematic illustration of an inverter arrangement according to one embodiment. The inverter arrangement can

for example, three half bridges with two semiconductor switches 3 each. Each of these semiconductor switches 3 can be controlled by a driver circuit 2. In addition, a protective device 1 according to one of the previously described embodiments can be provided for each driver circuit 2. In this way, individual protection can be provided for the driver circuits 2 of the semiconductor switch 3. Especially when in one of the

Semiconductor switch 3 a fault, in particular a short circuit between

Control connection and another connection occurs, the

corresponding driver circuit 2 by the corresponding

Protective device 1 can be deactivated. The operation of the

remaining semiconductor switch and the associated driver circuits 2 are not affected. In particular if the inverter circuit is provided, for example, to control an electrical machine, in the event of a fault in one of the semiconductor switches 3, the

Inverter arrangement can be transferred to a safe operating state.

For example, such a safe operating state can be an active short circuit in which all upper or lower

Semiconductor switches are closed at the same time. If, for example, 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 remaining two lower semiconductor switches can also be closed. The three upper semiconductor switches 3 are all opened. Analog can also be used for a Short circuit of one of the upper semiconductor switches 3 can be proceeded. By deactivating the driver circuit of a defective semiconductor switch 3, it is still possible to safely control the remaining semiconductor switches 3.

FIG. 4 shows a schematic representation of a flowchart on the basis of a method for protecting a driver circuit for controlling a semiconductor switch according to one embodiment. The method can in particular be applied to a driver circuit 2 for controlling a

Semiconductor switch 3 are used, the driver circuit 2 by means of an electrical series resistor 21 with a control terminal of the

Semiconductor switch 3 is electrically coupled. 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 characteristic has been detected in the detected voltage drop. As described above, the predetermined characteristic can be, for example, the voltage drop being exceeded over a

Act threshold for a predetermined period of time. 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 predefined threshold value and if the threshold value is exceeded for at least a predefined period of time, the control of the semiconductor switch can be deactivated. This deactivation can also be maintained if the detected voltage drop falls below the specified threshold value again.

In summary, the present invention relates to the protection of a

Driver circuit for controlling a semiconductor switch. For this purpose, a voltage drop in a series resistor between the driver circuit and a control connection of the semiconductor switch is evaluated. If the voltage drop across the series resistor exceeds a predetermined threshold value and this threshold value is exceeded for at least a predetermined period of time, the driver circuit for the semiconductor switch is then deactivated.

Claims

Expectations

1. Protection device (1) for a driver circuit (2) for controlling a semiconductor switch (3), wherein the driver circuit (2) by means of an electrical series resistor (21) with a control terminal of the

Semiconductor switch (3) is electrically coupled, the protective device (1) being designed to detect a voltage drop across the series resistor (21) of the driver circuit (2) and to deactivate the driver circuit (2) if it is detected

Voltage drop a predetermined characteristic has been detected.

2. Protection device (1) according to claim 1, with a low-pass filter (11) which is designed to detect the voltage drop across the

To filter series resistor (21).

3. Protection device (1) according to claim 1 or 2, with a

Comparison device (12) which is designed to compare a value of the detected voltage drop across the series resistor (21) with a predetermined threshold value.

4. Protection device (1) according to claim 3, wherein the predetermined

Threshold is adjustable.

5. Protection device (1) according to claim 4, wherein the predetermined

The threshold value can be adapted as a function of at least one supply voltage of the driver circuit (2).

6. Protection device (1) according to one of claims 3 to 5, with a

Storage device (13) which is designed to pass from a first state to a second state when the comparison device (12) has detected that the voltage drop has exceeded the predetermined threshold value.

7. Control device for a semiconductor switch (3), comprising: a driver circuit (2) which is designed to provide a control signal at a control input of the semiconductor switch (3), and a protective device (1) according to one of claims 1 to 6.

8. An inverter arrangement, comprising: a plurality of semiconductor switches (3-i), and a plurality of control devices according to claim 7, wherein each control device is designed to control at least one of the plurality of semiconductor switches (3-i).

9. Inverter arrangement according to claim 8, wherein for each

Semiconductor switch (3-i) of the plurality of semiconductor switches (3-i) a separate control device is provided.

10. A method for protecting a driver circuit (2) for controlling a semiconductor switch (3), wherein the driver circuit (2) by means of an electrical series resistor (21) with a control terminal of the

Semiconductor switch (3) is electrically coupled, the method comprising the following steps:

Detecting (Sl) a voltage drop across the series resistor (21) of the driver circuit (2); and

Deactivating (S2) the driver circuit (2) when a predetermined characteristic has been detected in the detected voltage drop.