阅读说明：本技术 用于半导体开关的保护设备和操控电路以及用于操控半导体开关的方法 (Protective device and control circuit for a semiconductor switch and method for controlling a semiconductor switch ) 是由 T·李希特 T·布鲁克豪斯 P·辛恩 于 2020-04-29 设计创作，主要内容包括：本发明涉及对于半导体开关进行保护免受过电压。为此,在半导体开关的输入端子处设置电容器件。流入所述电容器件中的电荷量被积分,以便在超过极限值时触发保护功能。(The invention relates to the protection of semiconductor switches against overvoltages. For this purpose, a capacitive device is provided at the input terminal of the semiconductor switch. The amount of charge flowing into the capacitive element is integrated in order to trigger a protective function when a limit value is exceeded.)

1. A protection device (1) for a semiconductor switch (3), having:

a capacitance device (11, 11a, 11 b);

an integrator (12, 12 b) which is designed to integrate the charging current into the capacitive component (11, 11a, 11 b) in order to determine the charge quantity (Q) in the capacitive component (11, 11a, 11 b) from the integrated charging current;

a comparison device (13) which is designed to actuate the semiconductor switch (3) when the determined charge quantity (Q) in the capacitive component (11, 11a, 11 b) exceeds a predefined limit value (S);

wherein the capacitance device (11, 11a, 11 b) is arranged between an input terminal (31) of the semiconductor switch (3) and the integrator (12, 12 b).

2. The protection device (1) as claimed in claim 1, wherein the capacitive means (11, 11a, 11 b) comprise a diode (11 a), in particular an avalanche diode.

3. The protection device (1) according to claim 2, wherein the predefined limit value (S) can be adjusted using a barrier capacitance of the diode (11 a).

4. The protection device (1) according to claim 2 or 3, wherein the comparison means (13) are designed for operating the semiconductor switch (3) when the voltage across the diode (11 a) exceeds the breakdown voltage of the diode (11 a).

5. The protection device (1) according to claim 1, wherein said capacitive means (11, 11a, 11 b) comprise a capacitor (11 b).

6. The protection device (1) according to any one of claims 1 to 5, wherein the integrator (12, 12 b) is designed for synchronizing the integration of the charging current with a control signal (D) for the semiconductor switch (3).

7. The protection device (1) as claimed in claim 6, wherein the integrator (12, 12 b) is designed to start the integration of the charging current when the semiconductor switch (13) is opened.

8. The protection device (1) according to any one of claims 1 to 7, wherein the integrator (12 b) comprises a capacitor.

9. A control circuit (2) for a semiconductor switch (3) has:

a drive circuit (20) which is designed to receive a control signal (D) for the semiconductor switch (3) and to actuate a control terminal (32) of the semiconductor switch (3) using the received control signal (D); and

the protection device (1) according to any one of claims 1 to 8,

wherein the drive circuit (20) is electrically coupled to the protective device (1) and the drive circuit (20) is designed to actuate the semiconductor switch (3) at least in part when the charge quantity (Q) in the capacitive component (11, 11a, 11 b) determined by the protective device (1) exceeds the predefined limit value (S).

10. Method for operating a semiconductor switch (3), having the following steps:

integrating (S1) a charging current into a capacitive device (11, 11a, 11 b) arranged between an input terminal (31) of the semiconductor switch (3) and an integrator (12, 12 b) in order to determine a charge amount (Q) in the capacitive device (11, 11a, 11 b) from the integrated charging current;

comparing (S2) the determined charge quantity (Q) in the capacitive component (11, 11a, 11 b) with a predefined limit value (S); and

-actuating (S3) the semiconductor switch (3) when the determined charge quantity (Q) in the capacitive component (11, 11a, 11 b) exceeds the predefined limit value (S).

11. The method according to claim 10, wherein the integration of the charging current is started when the semiconductor switch (3) is turned off (S1).

Technical Field

The invention relates to a protective device for a semiconductor switch and to a control circuit for a semiconductor switch. The invention further relates to a method for operating a semiconductor switch. In particular, the invention relates to protecting semiconductor switches from overvoltage.

Background

The use of semiconductor switches as switching elements is becoming more and more important. Here, when the switching element, in particular the semiconductor switching element, is turned off, an overvoltage may occur at the output of the semiconductor switch due to leakage inductance or the like. In order to avoid damage to the semiconductor switches due to such overvoltages, suitable overvoltage protection should be provided. Such overvoltage protection is known, for example, by the term "Active Clamping".

Publication DE 102013202641 a1 discloses overvoltage protection for semiconductor switches with static and dynamic components. For example, a dynamic component may respond in an overvoltage condition below a steady state value, and its response behavior is limited in time.

For protection devices of semiconductor switches, for example, avalanche diodes can be used to detect overvoltages. As the switching speed of semiconductor switches increases, the capacitive properties of such avalanche diodes must be taken into account more and more.

Disclosure of Invention

The invention creates a protective device for a semiconductor switch, an actuation circuit for a semiconductor switch and a method for actuating a semiconductor switch with the features of the independent patent claims. Other embodiments are the subject of the dependent patent claims.

Accordingly, provision is made for:

a protection device for a semiconductor switch has a capacitance element, an integrator and a comparison device. The integrator is designed to integrate the charging current into the capacitive device. In this way, the amount of charge in the capacitive device can be determined from the integrated charging current. In this case, the capacitance device is arranged between the input terminal of the semiconductor switch and the integrator. The comparison device is designed to actuate the semiconductor switch when the determined charge quantity in the capacitive element exceeds a predetermined limit value.

Furthermore, provision is made for:

a control circuit for a semiconductor switch has a drive circuit and a protective device according to the invention for the semiconductor switch. The driver circuit is designed to receive a control signal for the semiconductor switch and to actuate the control terminal of the semiconductor switch using the received control signal. The drive circuit is electrically coupled in particular to the protection device. The drive circuit is furthermore designed to actuate the semiconductor switch at least partially when the charge quantity in the capacitive component determined by the protective device exceeds a predefined limit value.

Finally, provision is made for:

a method for operating a semiconductor switch has a step of integrating a charging current in a capacitive element arranged between an input terminal of the semiconductor switch and an integrator. The charge amount in the capacitive device is determined by integrating the charging current. The method further comprises the steps of comparing the determined charge quantity in the capacitive element with a predefined limit value and actuating the semiconductor switch when the determined charge quantity in the capacitive element exceeds the predefined limit value.

Advantages of the invention

Conventional overvoltage protection devices for semiconductor switching elements typically use a clamping diode, such as an avalanche diode or a zener diode. As the switching speed increases, the capacitance characteristics, in particular the barrier capacitance of such diodes, must also be taken into account in this case. Depending on the design, the capacitive properties may have a negative influence on the response voltage or the response behavior of the overvoltage protection device for semiconductor switches.

The idea of the invention is therefore to take this knowledge into account and to provide a protective device for a semiconductor switch, which protective device specifically takes into account the capacitive behavior of the component for detecting overvoltages. In this way, in particular even at high switching speeds, an overvoltage at the semiconductor switching element can be reliably and quickly detected. Accordingly, the occurrence of overvoltage can be recognized early, and appropriate countermeasures can be taken to avoid the overvoltage. For example, the semiconductor switching element may be fully or partially closed in order to resist a further increase in the voltage across the terminals of the semiconductor switching element. Damage to the semiconductor switching element or at least premature aging due to overvoltages or the like can thereby be prevented.

If the capacitance of the capacitive device is known, the amount of charge in the capacitive device can be determined by integrating the current into the capacitive device. The voltage at the semiconductor switching element can thus be derived from the relation between the capacitance of the capacitive device and the determined amount of charge. If the determined amount of charge in the capacitive device exceeds the amount of charge corresponding to the predefined trigger voltage, appropriate measures can be taken in order to raise or lower the voltage across the semiconductor switching element against a further voltage at the semiconductor switching element. For example, the semiconductor switching elements can be fully or partially actuated or closed for this purpose.

In this case, especially at high switching speeds, the evaluation of the amount of charge in the capacitive device enables a rapid and efficient detection of potential overvoltages at the semiconductor switching element.

According to an embodiment, the capacitive device comprises a diode. In particular, the capacitive device may for example comprise an avalanche diode or a zener diode. Diodes with a defined breakdown voltage, such as avalanche diodes or zener diodes, make it possible to detect overvoltages even in the case of slow or static voltage increases. In addition, however, at higher switching speeds, the capacitance properties, such as the barrier capacitance of the diode, must also be taken into account. By evaluating the amount of charge entering the diode before the blocking layer capacitance of the diode is charged and the diode is excited, the reaching of a critical overvoltage can already be detected. Accordingly, reliable overvoltage protection can be ensured both in the case of slow switching processes and also in the case of rapid switching processes.

According to one specific embodiment, the predefined charge amount can be set using the barrier capacitance of the diode. For example, the barrier capacitance may be determined based on the specifications in the data table for the corresponding diode. Furthermore, any other method, in particular a measurement-technical method for determining the barrier capacitance of the respective diode, is of course also possible. By taking into account the barrier capacitance, the response of the protection device for protecting the semiconductor switch can be precisely adjusted. For example, based on the barrier layer capacitance and a predefined voltage threshold for the protective device, the charge quantity can be determined, in particular calculated, at which the protective device is to be triggered.

According to one specific embodiment, the comparator is designed to actuate the semiconductor switch when the voltage across the diode exceeds the breakdown voltage of the diode. In particular, the breakdown voltage may be a breakdown voltage in the blocking direction of an avalanche diode or a zener diode. In this way, the semiconductor switch is actuated if a predefined breakdown voltage of the diode in the blocking direction is exceeded, even if the determined charge quantity has not reached a predefined limit value by the time. The reliability of the protection function can thereby still be further improved.

According to an embodiment, the capacitive device comprises a capacitor. Capacitors are simple to implement and low cost devices. By using a capacitor, an inexpensive, simple and reliable protection device for a semiconductor switch can thereby be realized.

According to one embodiment, the integrator is designed to synchronize the integration of the charging current with the control signal for the semiconductor switch. For example, the integrator may be reset in synchronization with the control signal for the semiconductor switch. In this way, drift of the integrator during integration of the charging current can be avoided.

According to one embodiment, the integrator is designed to restart the integration of the charging current each time the semiconductor switch is opened. At the start of the integration, the values of the integrators can be reset, respectively. In this way, when the semiconductor switch is switched off, the integration of the charging current starts at a defined zero value and the voltage across the semiconductor switch therefore rises.

According to one embodiment, the integrator may comprise a capacitor. In particular, the integrator may be composed of one capacitor or a device having a plurality of capacitors. The capacitive component, in particular the capacitor, enables a particularly simple integration of the charge quantity. Here, the voltage applied to both terminals of the capacitor may correspond to the amount of charge in the capacitor.

The above-described configurations and modifications can be combined with one another as far as they are relevant. Other configurations, modifications and implementations of the invention also include combinations of features of the invention not explicitly mentioned previously or in the following with respect to the embodiments. In particular, the person skilled in the art will here also add individual aspects as an improvement or supplement to the corresponding basic form of the invention.

Drawings

Further features and advantages of the invention are set forth below with reference to the drawings. Here:

fig. 1 shows a schematic diagram of a circuit schematic of a control circuit for a semiconductor switch with a protective device according to an embodiment;

fig. 2 shows a schematic diagram of a circuit schematic of a control circuit for a semiconductor switch according to a further embodiment;

fig. 3 shows a schematic diagram of a circuit schematic of a control circuit for a semiconductor switch according to a further embodiment; and

fig. 4 shows a schematic illustration of a flow chart as a basis for a method for actuating a semiconductor switch according to an embodiment.

Detailed Description

Fig. 1 shows a schematic diagram of a circuit schematic of a control circuit 2 for a semiconductor switch 3. The control circuit 2 comprises a drive circuit 20 for driving a control terminal 32 of the semiconductor switch 3. For this purpose, the driver circuit 20 receives a control signal D, amplifies it and actuates the control terminal 32 of the semiconductor switch 3 as a function of the control signal D. In this way, the electrical connection between the input terminal 31 and the output terminal 33 of the semiconductor switch 3 can be opened or closed. The semiconductor switch 3 may be, for example, a MOSFET or a bipolar transistor (IGBT) having an insulated gate terminal. Of course, in principle any other semiconductor switch is also possible. For example, the semiconductor switch 3 may be a semiconductor switch of a power stage (e.g., a rectifier, etc.). If the electrical connection between the input terminal 31 and the output terminal 33 of the semiconductor switch 3 is interrupted, a voltage rise between the input terminal 31 and the output terminal 32 may occur, for example, due to leakage inductance. The semiconductor switch 3 can thus be damaged or, if necessary, can even be destroyed if the voltage between the input terminal 31 and the output terminal 32 rises beyond a permissible level. To prevent such overvoltages, a protective device 1 may be provided, for example.

The protection device 1 comprises a capacitance device 11, an integrator 12 and a comparison means 13. The protection device 1 may also comprise, for example, logic gates 14 and, if necessary, further components. The capacitance device 11 is arranged between the input terminal 31 of the semiconductor switch and the input terminal of the integrator 12. If the voltage at the input terminal 31 of the semiconductor switch 3 rises, the capacitive device 11 is charged via the integrator 12. Here, the integrator 12 integrates the charging current into the capacitive device. By such integration, the integrator 12 can determine the amount of charge flowing into the capacitive element 12. In the case where the capacitance C of the capacitance device 11 is constant, the amount of charge in the capacitance device 11 is therefore proportional to the voltage across the capacitance device 11.

The integrator 12 outputs an output signal proportional to the determined charge amount Q in the capacitance device 11. In this case either an analog or a digital output signal. In this way, the determined charge amount Q is supplied to the comparator 13. The comparator 13 compares the determined charge quantity Q with a predefined limit value S. For example, the comparator 13 can be a subtractor which forms the difference between the determined charge quantity Q and a predefined setpoint value S. If the determined charge amount Q exceeds a predefined setpoint value S, the control input 32 of the semiconductor switch 3 can then be actuated, for example. In this way, the semiconductor switch 3 can be fully or at least partially rendered conductive between the input terminal 31 and the output terminal 33. Thereby reducing the voltage between input terminal 31 and output terminal 32. For example, the control terminal 32 of the semiconductor switch 3 can likewise be controlled by the driver circuit 20.

Furthermore, the actuation of the semiconductor switch 3 can be additionally associated with the actuation signal D after the detection of the determined charge quantity exceeding the setpoint value S. For this purpose, the result of the comparator 13 and the control signal D can be supplied to the logic gate 14. The logic gate 14 correlates the result of the comparator 13 and the steering signal D with each other. For example, the semiconductor switch 3 can be actuated only if the semiconductor switch is not actuated according to the control signal D, but the comparator 13 determines that the charge quantity Q exceeds the setpoint value S. However, as long as the control signal D specifies an active actuation of the semiconductor switch 3, no further influence is exerted by the protection device 1.

The integrator 12 may be any analog or digital integrator. The integrator 12 may be implemented, for example, by means of any known or novel integrator circuit.

Furthermore, the integration of the integrator 12 can be synchronized with the steering signal D. For example, if the semiconductor switch 12 should be opened in accordance with the manipulation signal D, the integration of the integrator 12 may be reset and restarted, respectively. In this way, for example, drift of the integrator can be avoided. Furthermore, any other synchronization of the integrator 12 is of course also possible, in particular in the case of the use of the control signal D.

Fig. 2 shows a schematic diagram of a circuit schematic of a control circuit 2 for a semiconductor switch 3 according to a further embodiment. The control circuit 2 and in particular the protection device 1 corresponds to the above-described embodiment to the greatest extent. The embodiment according to fig. 2 differs from the above-described embodiments in particular in that the capacitive component 11 is a diode 11 a. The diode 11a may be an avalanche diode or a zener diode, for example. Such a diode 11a may have a defined breakdown voltage at which the diode 11a becomes conductive even in the off direction. However, the diode 11a also has a capacitive characteristic before the diode is turned into a conductive state. Before breaking down the diode 11a, the barrier capacitance of the diode 11a is charged here. The integrator 12 integrates the charging current into the diode 11a and accordingly forwards the determined charge quantity Q to the comparator 13. If the charge quantity Q is detected to exceed a predefined setpoint value S, the semiconductor switch 3 can be actuated, as already described above. Furthermore, the semiconductor switch 3 can also be activated when the diode 11a is switched into the conductive state after the breakdown voltage has been exceeded. For this purpose, the terminal of the diode 11a connected to the integrator 12 is additionally also connected to a further driver stage 15, which outputs an output signal for actuating the semiconductor switch 3 after breaking down the diode 11 a. The output of the comparator 13 is also connected, if necessary, via the above-mentioned logic gate 14 to the further driver stage 15. In this way, in the case of a fast dynamic process, overvoltage protection can be achieved by evaluating the amount of charge in the diode 11 a. Furthermore, even in the case of slow, if necessary static, overvoltages, the triggering of the protective device can be effected by the activation of the (zenden) diode 11 a.

Fig. 3 shows a further embodiment of a control circuit 2 for a semiconductor switch. In this embodiment, the capacitance device 11 includes a capacitor 11 b. Accordingly, by integrating the charging current into the capacitor 11b and comparing the amount of charge from the integrated charging current with the rated value S, overvoltage protection can be achieved. If necessary, the integrator 12 can be implemented, for example, as a capacitor 12b in a simple embodiment. Such a circuit arrangement with the two capacitors 11b and 12b as capacitance elements and integrators enables particularly simple and therefore cost-effective overvoltage protection for the semiconductor switch 3.

Fig. 4 shows a schematic illustration of a flow chart as a basis for a method for actuating the semiconductor switch 3 according to an embodiment. The method may in principle comprise suitable method steps of each type as have been described previously in connection with the protection device 1 and the control circuit 2. Furthermore, the protection device 1 and the control circuit 2 may also comprise any suitable components to implement the method steps described subsequently.

The method includes a step S1 for integrating the charging current into the capacitance device 11. The capacitance device may be arranged between the input terminal 31 of the semiconductor switch 3 and the integrator 12. In this way, the amount of charge Q in the capacitive device 11 can be determined from the integrated charging current. The method further comprises a step S2 for comparing the determined charge quantity Q in the capacitive component with a predefined limit value S. Finally, the method comprises a step S3 for actuating the semiconductor switch 3 when the determined charge quantity Q in the capacitive element 11 exceeds a predefined limit value S.

In particular, the integration of the charging current can be synchronized with the control signal D for the semiconductor switch 3. For example, when the semiconductor switch 3 is closed, the integration of the charging current may be reset and started.

In summary, the invention relates to the protection of semiconductor switches against overvoltages. For this purpose, a capacitive device is provided at the input terminal of the semiconductor switch. The amount of charge flowing into the capacitor device is integrated in order to trigger a protective function when a limit value is exceeded.