EP4035268A1

EP4035268A1 - Circuit arrangement for controlling a plurality of semiconductor switches connected in parallel

Info

Publication number: EP4035268A1
Application number: EP20764369.3A
Authority: EP
Inventors: Calin Purcarea; Tobias Richter; Matthias Boesing; Tim Bruckhaus; Daniel Schweiker
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2019-09-24
Filing date: 2020-08-28
Publication date: 2022-08-03
Also published as: CN114667680A; DE102019214539A1; WO2021058227A1; US20220345125A1

Abstract

The invention relates to a circuit arrangement (200) for controlling a plurality of semiconductor switches connected in parallel, having an activation connection (213) and a deactivation connection (214), and having a plurality of control connections (220), each provided for connection to a control connection (123) of one of the plurality of semiconductor switches, wherein the activation connection (213) and the deactivation connection (214) are each connected to each of the plurality of control connections (220), and wherein a circuit breaker (230) is provided between the activation connection (213) and at least one of the control connections (220), furthermore having at least one detection and control arrangement which is designed to detect a current flow in the at least one of the control connections (220) and, if a short-circuit is detected on the basis of the current flow, to control the circuit breaker (230) to open.

Description

description

title

Circuit arrangement for controlling several semiconductor switches connected in parallel

The present invention relates to a circuit arrangement for controlling a plurality of semiconductor switches connected in parallel, an arrangement with several semiconductor switches connected in parallel and such a circuit arrangement and a use of such a circuit arrangement.

State of the art

Special circuit arrangements, so-called gate driver ICs (integrated circuits) can be used to control (or switch on and off) semiconductor switches. Depending on the performance of the semiconductor switches to be controlled, large control currents, for example in the double-digit ampere range, are sometimes necessary. A so-called booster unit, for example, can be used as part of the gate driver IC or in addition to generate such high control currents.

In high-performance applications, several semiconductor switches sometimes have to be connected in parallel in order to provide the required current-carrying capacity. For example, when operating electrical machines, converters connected in parallel, for example in the form of bridge circuits (e.g. so-called B6 bridge), can be used to convert either an AC voltage generated by the electrical machine into a DC voltage or a DC voltage for operation to convert an electrical machine into an alternating voltage. Then the converter is referred to as a rectifier or an inverter. The converters include also, for example, frequency converters to convert an alternating voltage into an alternating voltage with a different frequency.

Here it can happen that a single semiconductor switch suffers a failure, which is typically associated with a short circuit in the half-bridge when the series-connected semiconductor switch in the half-bridge is or is switched to be conductive. Ultimately, this can lead to a fire in the corresponding power electronics or to an undesired torque setting in an electrical machine.

To avoid this, the serially connected semiconductor switch in the half-bridge should be disconnected and a safe state, e.g. an active short circuit, in which all semiconductor switches on one side (low side or high side, expediently the side with the defective semiconductor switch) should be are closed or switched to conduct.

If a short circuit also occurs at the gate of the defective semiconductor switch, however, a voltage supply, e.g. via the booster unit, can be short-circuited in such a circuit arrangement. Depending on the supply concept, this also couples to the gate driver supply of a semiconductor switch on the same side of the bridge circuit, i.e. high side or low side, and also short-circuits it, which prevents the active short circuit from being set.

Disclosure of the invention

According to the invention, a circuit arrangement for controlling several semiconductor switches connected in parallel, an arrangement with several semiconductor switches connected in parallel and with such a circuit arrangement and the use of such a circuit arrangement for controlling several semiconductor switches connected in parallel are proposed with the features of the independent claims. Advantageous refinements are the subject matter of the subclaims and the description below. The invention relates to a circuit arrangement for controlling several, ie two or more parallel-connected semiconductor switches, in particular power semiconductors such as MOSFETs or IGBTs. The circuit arrangement has a switch-on connection and a switch-off connection, as well as a plurality of control connections which are each provided for connection to a control connection, in particular a gate connection or a gate, of one of the several semiconductor switches. The switch-on connection is understood to mean a connection for a potential which switches the semiconductor switch to the conductive state, and the switch-off connection is understood to be a connection with a potential that switches the semiconductor switch to a blocking state. When used, the switch-on connection and the switch-off connection are typically connected to a so-called gate driver, possibly with a suitable booster unit interposed, which make the mentioned potentials available.

The switch-on connection and the switch-off connection are each connected to each of the multiple control connections, i.e. the corresponding control connections are connected in parallel and the corresponding semiconductor switches or their gates can be controlled in parallel. In the case of a path between the switch-on connection and the control connection, this is typically referred to as a switch-on path, and in the case of a path between the switch-off connection and the control connection, a switch-off path.

In the proposed circuit arrangement, an isolating switch is now also provided between the switch-on connection and at least one of the plurality of control connections. In this case, however, it is preferred if a circuit breaker is provided between the switching connection and each of the control connections. In addition, the circuit arrangement has at least one detection and control arrangement which is set up to detect a current flow into or out of the at least one of the control connections - for example via a voltage drop across a resistor in the control path - and if a short circuit is detected or . can be closed to a short circuit - to trigger the disconnector to open it. Here, too, it is advantageous to provide such a detection and control arrangement for each circuit breaker in the case of several such disconnectors. On the basis of the current flow in the control path, a short circuit can in particular be detected when the current flow exceeds a predetermined threshold value for at least a predetermined period of time. It should be noted here that a high current can flow into or out of the control connection even during regular operation, but then only for a short time. A longer lasting, high current, however, suggests a short circuit. This can be implemented, for example, by using a low-pass filter in front of a comparator, by means of which short-term high currents are masked out.

At the comparator itself, the current flow only has to exceed or fall below a threshold value, based on the input differential voltage of the comparator.

It is useful here if the at least one detection and control arrangement has a detection unit and a control unit, the detection unit being set up to detect the flow of current into or out of the corresponding control connection, and the control unit being set up to control the to control the corresponding isolating switch to open it when a short circuit at the control connection has been detected (possibly by means of the detection unit). In the case of several detection and control arrangements, this applies accordingly to each of them.

In this way, a possibility is provided to decouple the defective semiconductor switch or a corresponding chip or a corresponding module (depending on the type of division of the gate signals). This prevents crosstalk to an adjacent semiconductor switch, and semiconductor switches that are still intact can continue to be controlled in order to distribute a current flowing due to the active short circuit and to minimize the load on the construction and connection technology, in particular the bonding wires, as far as possible and a To prevent fire or the like.

A diode is preferably also provided between the switch-off connection and the at least one of the drive connections, the direction of which is in the direction of the switch-off connection. It is also useful here if between see the switch-off connection and each of the control connections such a diode is provided. In this way, the multiple control connections or the gates of the corresponding semiconductor switches can be locked against one another.

The invention also relates to an arrangement with a plurality of semiconductor switches connected in parallel and with a circuit arrangement according to the invention, the control terminals of the circuit arrangement being each connected to a control terminal of one of the plurality of semiconductor switches. The plurality of semiconductor switches connected in parallel are preferably designed to be at least part of a converter, for example a bridge circuit. Such an arrangement can, for example, be part of power electronics for controlling an electrical machine. The subject of the inven tion is also power electronics with such an arrangement, for example a bridge circuit, a power converter, an inverter, etc.

The invention furthermore relates to the use of a circuit arrangement according to the invention for controlling a plurality of semiconductor switches connected in parallel, with the detection and control arrangement being used to detect a current flow into or out of the at least one of the control connections and, if the current flow exceeds a predetermined threshold value, the disconnector is triggered to open.

Further advantages and embodiments of the invention emerge from the description and the accompanying drawings.

The invention is illustrated schematically using an exemplary embodiment in the drawing and is described below with reference to the drawing.

Brief description of the drawings

Figure 1 shows schematically an arrangement according to the invention in a preferred embodiment for controlling an electrical machine. Figure 2 shows schematically part of a circuit arrangement according to the invention in a preferred embodiment.

Figure 3 shows schematically part of a circuit arrangement according to the invention in a further preferred embodiment.

Figure 4 shows schematically a further part of a circuit arrangement according to the invention in a preferred embodiment.

Figure 5 shows schematically a further part of a circuit arrangement according to the invention in a preferred embodiment.

Embodiment (s) of the invention

In Figure 1, an arrangement according to the invention in a preferred embodiment for controlling an electrical machine 100 is shown schematically. The arrangement here comprises a circuit arrangement 200, which is only indicated here and is explained in more detail with reference to the following figures, as well as a power converter 110 embodied as a so-called B6 bridge by way of example.

The converter 110 has two DC voltage connections 131, 132, which are connected in the usual way, in addition to a capacitor, with, for example, six semiconductor switches 120, for example MOSFETs. A phase of the electrical machine 100 is connected between each two of the semiconductor switches 120.

Each of the semiconductor switches 120 has a drain connection 121, a source connection 122 and a control connection or gate connection 123. The semiconductor switches 120 are each constructed in the same way.

During operation of the converter 110, the individual semiconductor switches 120 are now controlled in a suitable manner for opening or closing. For this purpose, the circuit arrangement 200 is used, which is connected to the corresponding Control connections 123 is connected. In the case of a conventional control, one switch is always closed and the other is open for each branch, for example.

In FIG. 2, part of a circuit arrangement 200 according to the invention is shown schematically in a preferred embodiment for controlling several, here two, semiconductor switches connected in parallel. The circuit arrangement 200 has a switch-on connection 213 and a switch-off connection 214 for connection to suitable switching potentials, which are provided here, for example, by a booster unit 210, which in turn has a positive supply connection 211 and a negative supply connection 212 for connection to a gate driver. The booster unit 210 can be part of the gate driver, or the booster unit 210 is preceded by the gate driver.

The switch-on connection 213 and the switch-off connection 214 are each connected to two control connections 220, for example. Each of the control connections 220 is provided to be connected to a corresponding connection or gate connection 123 of a semiconductor switch, such as a semiconductor switch 120 according to FIG. 1. The semiconductor switches are controlled in parallel in this way, for example to control two B6 bridges in parallel.

The connection between the switch-on terminal 213 and an Ansteueran circuit 220 defines a switch-on path, ie the gate of the semiconductor switch can thus be placed on a potential that turns the semiconductor switch on, and the connection between the switch-off terminal 214 and the drive terminal 220 defines a Switch-off path, ie the gate of the semiconductor switch can thus be placed on a potential which switches the semiconductor switch to a blocking state.

_{In addition, a switch-on resistor R on is} provided in the switch-on path or between switch-on connection 213 and control connection 220, and a switch- _{off resistor R 0ff is} provided in the switch-off path or between switch-off connection 214 and control connection 220. Furthermore, a disconnection switch 230, for example a MOSFET, is provided in each switch-on path, ie between switch-on connection 213 and control connection 220, by means of which control connection 220 can be disconnected from switch-on connection 213. Each isolating switch 230 has a control connection or gate connection 231 to which a control unit 260 is connected, which is only indicated schematically here. This control unit 260 is in turn connected to a detection unit 280, which is used to detect a short circuit and is also only indicated schematically.

The control unit 260 and the detection unit 280, which together form a detection and control unit, are explained in more detail with reference to the following figures.

In Figure 3, a part of a circuit arrangement 200 'according to the invention is shown schematically in a further preferred embodiment. The basic principle of the circuit arrangement 200 'corresponds to the circuit arrangement 200 according to FIG. 2, so that in this respect reference can also be made to the description there. Here, however, only one control connection 220 is shown as an example, a capacitor 232 being provided between the switch-on connection 213 and a control connection 231 of the isolating switch 230. This prevents the isolating switch 230 from being inadvertently switched off in the event of a pulsed operation of the booster unit 210 during an off phase. To control a plurality of semiconductor switches, a plurality of such circuit arrangements 200 ′ must accordingly be connected to the switch-on connection 213 and the switch-off connection 214. The resistor connected in parallel to the capacitor 232 ensures a defined potential at the gate of the isolating switch 230 when the circuit is started up, as well as a safe blocking state.

During operation, the isolating switch 230 is installed in series with the switch- _on resistor R on (here several resistors are connected in parallel to increase the current-carrying capacity), by means of which a defective semiconductor switch can be disconnected in the event of a fault. A so-called charge pump can be generated with a diode 262 (see FIG. 4) in the control unit, which enables voltages at the control connection 231 below the negative supply voltage (see connection 212) and thus the channel of the isolating switch 230 in cyclic operation even when the supply voltage is negative Keeps voltage at control connection 220 closed.

The gate of the semiconductor switch to be decoupled is discharged via the switch-off _resistor R 0f r (here several resistors are connected in parallel to increase the current-carrying capacity) and the diode 235. The diode 235 also serves to transfer a cross current from a still functioning semiconductor switch to the parallel, but to prevent a defective semiconductor switch or its gate path via the switch-off resistors.

In Figure 4, a further part of a circuit arrangement according to the invention is shown schematically in a preferred embodiment, namely a control unit 260, as can be used, for example, in the circuit arrangement 200 according to FIG. 2 or the circuit arrangement 200 'according to FIG.

If the relevant semiconductor switch to be monitored is not in a fault condition, the input of the control unit (connection to detection unit 280) is at low potential, and thus semiconductor switch 261, for example a MOSFET, is permanently switched on or conductive.

As a result, ground potential is applied to the gate or control connection 231 of the isolating switch, which is why this is activated when the booster unit is switched on. The diode 262 prevents a capacitance of the control connection 231 from being discharged via the control unit or the control circuit when the booster unit is switched on and off cyclically in the cyclic operation.

In the event of a fault, ie if, for example, a short circuit is detected on the relevant semiconductor switch, the input of the control unit is at high potential and the semiconductor switch 261 is switched off and the semiconductor switch 263 264, for example transistors, are switched on or conductive. In this way, the control connection 231 or the gate of the isolating switch is quickly charged to the potential of the switch-on output 213 of the booster unit. The isolating switch 230 is thus opened and the defective semiconductor switch is decoupled.

In Figure 5, a further part of a circuit arrangement according to the invention is shown schematically in a preferred embodiment, namely a detection unit 280, as it is, for example, in the circuit arrangement 200 according to FIG. 2, the circuit arrangement 200 'according to FIG. 3 or with the control unit 260 according to FIG 4 can be used.

During operation, a current flow into or out of the gate (control connection 220) is monitored, here by means of a voltage drop across the switch- _on resistor R on (see FIGS. 2 and 3) via the connections 216 and 220 compared with a reference value or threshold value. Targeted switching operations of the semiconductor switch can be masked out by means of a low-pass filter, ie a (with under high) current flow during a (regular) switching operation is not taken into account or not recognized as a short circuit in order to prevent false tripping.

A recognized error state, i.e. when the voltage drop exceeds the reference value or threshold value at the comparator, can be locked ("spawned" or so-called "latch function") by feeding back the output signal of the comparator via the diode 282 and the resistor 283, ie the control unit 260 can permanently receive a corresponding signal or a corresponding voltage level in order to open the circuit breaker. The reference value or threshold value can be selected in such a way that when it is exceeded it can be assumed that a short circuit is present. Each semiconductor switch preferably has a separate detection unit for its switch-on resistance. At this point it should be noted that further components shown in the circuits of FIGS. 3 to 5 are standard components and are therefore in some cases not designated or explained in more detail. For example, the two resistors at the connections 216, 220 and the capacitance at the inputs of the comparator 281 serve as the already mentioned low-pass filter upstream of the comparator.

The two resistors at the left connection 211 and the connection 212 are used, for example, to set a response threshold based on a differential voltage at the input of the comparator 281. The transistor 284 with the two upstream resistors is used to amplify the output power of the comparator 281.

Claims

Expectations

1.Circuit arrangement (200, 200 ') for controlling several semiconductor switches (120) connected in parallel, with a switch-on connection (213) and a switch-off connection (214), and with several control connections (220), each for connection to a control connection ( 123) one of the plurality of semiconductor switches (120) are provided, wherein the switch-on connection (213) and the switch-off connection (214) are each connected to each of the plurality of control connections (220), and wherein between the switch-on connection (213) and at least one of the control connections ( 220) an isolating switch (230) is provided, furthermore with at least one detection and control arrangement (260, 280) which is set up to detect a current flow in the at least one of the control connections (220) and, if based on the current flow, a Short-circuit is detected, trigger the disconnector (230) to open.

2. Circuit arrangement (200, 200 ') according to claim 1, wherein the at least one detection and control arrangement (260, 280) is set up to use the current flow to detect a short circuit when the current flow exceeds a predetermined threshold value for at least a predetermined period of time exceeds.

3. Circuit arrangement (200, 200 ') according to claim 1 or 2, wherein between the switch-off connection (214) and the at least one of the Ansteueran connections (220) a diode (235) is provided, the forward direction of which is in the direction of the switch-off connection (214) .

4. Circuit arrangement (200, 200 ') according to one of the preceding claims, wherein between the switch-on connection (213) and each of the Ansteueran connections (220) each have a circuit breaker (230) is provided.

5. Circuit arrangement (200, 200 ') according to claim 4, with a plurality of detection and control arrangements (260, 280), each of which is set up to record the current flow in the corresponding one of the control connections (220) and, if based on the current flow A short circuit is detected in the corresponding control connection (220), the corresponding disconnection switch (230) must be activated to open it.

6. Circuit arrangement (200, 200 ') according to one of the preceding claims, wherein the at least one detection and control arrangement has a detection unit (280) and a control unit (260), the detection unit (280) being set up to control the flow of current to detect the corresponding control connection (220) in the and to detect a short circuit based on the current flow, and wherein the control unit (260) is set up to open the corresponding disconnector (230) when a short circuit has been detected.

7. Circuit arrangement (200, 200 ') according to one of the preceding claims, wherein a capacitor (232) is provided between the switch-on connection (213) and an Ansteueran circuit (231) of the isolating switch (230).

8. Arrangement with a plurality of semiconductor switches (120) connected in parallel and with a circuit arrangement (200, 200 ') according to one of the preceding claims, wherein the control connections (220) of the circuit arrangement (200, 200') each have a control connection (123) of one of the a plurality of semiconductor switches (120) are connected.

9. The arrangement according to claim 8, wherein the plurality of semiconductor switches (120) connected in parallel are designed at least as part of a power converter.

10. Use of a circuit arrangement (200, 200 ') according to one of claims 1 to 7 for controlling a plurality of semiconductor switches (120) connected in parallel, with a current flow in the at least one of the control connections by means of the detection and control arrangement (260, 280) (220) is detected and, if a short circuit is detected on the basis of the current flow, the isolating switch (230) is triggered to open.