DE102022203310A1 - Electrical circuit arrangement for a surge protection system - Google Patents

Abstract

The present invention relates to an electrical circuit arrangement for an overvoltage protection system for a circuit which has a parasitic inductance during a switch-off process, the electrical circuit arrangement comprising: a first switching device (14) with a first connection (4) and a third connection (16), wherein A first varistor (3) is connected parallel to the first switching device (14), and a second switching device (15) with a second connection (8) and a fourth connection (17), with a second one parallel to the second switching device (15). Varistor (7) is connected, and the third connection (16) of the first switching device (14) is connected via an electrical conductor (9) to the fourth connection (17) of the second switching device (15).

Description

State of the art

The present invention relates to an electrical circuit arrangement for an overvoltage protection system for a circuit which has a parasitic inductance during a switch-off process, and to a method for operating the electrical circuit arrangement.

Protective circuits are known in the prior art, which protect electrical components of a switching device from parasitic inductances during a switch-off process. The induced voltage is created by the inductance in the event of a short circuit, for example. For example, (TVS) diodes can be used as a protective circuit. Alternatively, the use of active clamping or avalanche is known, whereby MOSFETs are operated in the linear range or avalanche in order to dissipate the heat in the MOSFETs. Furthermore, the use of an R-C element in parallel to the switch (snubber) as a protective circuit and the method “Voltage Overshoot Suppression for SiC MOSFET-Based DC Solid-State Circuit Breaker” are known in the prior art.

DE 10 2016 011 815 B3 discloses a protection circuit for controlling intelligent lamps, for example to protect against lightning strikes. Varistors are used in individual exemplary embodiments.

DE 18 11 642 B2 discloses a protection circuit for a horizontal deflection system for a cathode ray tube, wherein a protection device switches off a pulse generating circuit when the magnitude of a current in a transformer is outside a predetermined range.

DE 27 53 171 discloses a device for protecting electrical systems against overvoltage. A first derivation element, an induction coil and a second derivation element are provided for each wire. Due to inertia, the first derivative element is only suitable for certain voltage ranges. Voltage peaks underneath are dissipated by the second derivation element.

Disclosure of the invention

The electrical circuit arrangement according to the invention for an overvoltage protection system for a circuit that has a parasitic inductance during a switch-off process with the features of claim 1 is characterized in that the overvoltages that arise during switch-off processes of circuits that have parasitic inductances are caused by the arrangement of varistors, i.e. voltage-dependent resistors, be dismantled, thereby ensuring cost-effective and space-saving overvoltage protection of the switching device to be protected. By using voltage-dependent resistors, easy adjustment to different voltage or current levels is also possible.

• - eine erste Schalteinrichtung mit einem ersten Anschluss und einem dritten Anschluss, wobei
• - parallel zu der ersten Schalteinrichtung ein erster Varistor angeschlossen ist, und
• - eine zweite Schalteinrichtung mit einem zweiten Anschluss und einem vierten Anschluss, wobei
• - parallel zu der zweiten Schalteinrichtung ein zweiter Varistor angeschlossen ist, und
• - die erste Schalteinrichtung mit dem dritten Anschluss über einen elektrischen Leiter mit dem vierten Anschluss der zweiten Schalteinrichtung verbunden ist.

The electrical circuit arrangement includes

• - a first switching device with a first connection and a third connection, wherein
• - A first varistor is connected in parallel to the first switching device, and
• - a second switching device with a second connection and a fourth connection, wherein
• - A second varistor is connected in parallel to the second switching device, and
• - The first switching device with the third connection is connected to the fourth connection of the second switching device via an electrical conductor.

A varistor/surge protector is in particular a voltage-dependent resistor. The resistance of the varistor decreases above a predefined voltage (threshold voltage) and the applied current can flow through the varistor. In this way, a varistor can absorb the current intensity in particular. Inductances in the system (e.g. through an energy storage device, electronic lines, busbar, etc.) and the shutdown current mainly define the energy that must be absorbed by the protective circuit: E = ½ *L*I ² , where the pulse length is “tau” via the quotient the system inductance and the system resistance are calculated: $$\text{dew}=\text{L\_sys}/\text{R\_sys}\text{.}$$

The circuit arrangement according to the invention can be used, for example, in a circuit of an energy storage device (accumulator, battery or in conjunction with an energy storage device). Additionally or alternatively, the circuit arrangement according to the invention can be used in a circuit of an electrical system. The first connection can preferably connect a first energy storage device to the first switching device. The first switching device can additionally or alternatively be connected to a first system. A fifth switch, in particular a semiconductor switch, can additionally be arranged between the first system and the first switching device. Additionally or alternatively, the second connection can connect the first energy storage device to the second switching device. The second switching device can additionally or alternatively be connected to the first system. A sixth switch, in particular a semiconductor switch, can additionally be arranged between the first system and the second switching device. The circuit arrangement preferably results in the energy of parasitic inductances being dissipated via the first varistor and not via the first switching device or via the second varistor and not via the second switching device during a switch-off process (short circuit).

Additionally or alternatively, the switching device can comprise further varistors, which are arranged parallel to the first varistor or to the second varistor. The selection of the number of additional varistors, which are arranged in parallel to the switching device to be protected, should preferably take into account the circuit requirements and the current strength. The integration of additional varistors connected in parallel leads to a reduction in the clamping voltage.

kann insbesondere die Integration eines Kondensators dienlich sein. Zusätzlich oder alternativ kann die Integration eines Kondensators für 800V-Systeme dienlich sein, wenn L_SYS < 6µH und für 400V-Systeme dienlich sein, wenn L_SYS < 3µH, wobei L_SYS eine durch einen Energiespeicher, Kabel und/oder Stromschienen in das elektrische System eingetragene Induktivität repräsentiert.The circuit arrangement according to the invention is particularly suitable for protecting electrical components of faulty circuits during shutdown processes (eg short circuit). The circuit arrangement is particularly suitable for use with very high switch-off energy pulses (for example several hundred joules). The electrical circuit arrangement according to the invention can also be easily adapted for the respective use in a circuit by adapting the dimensioning of the first varistor or the second varistor, with particular consideration of the electrical components to be protected. By means of suitable dimensioning, for example, switching devices in circuits for high voltages (e.g. up to 1000V or more) can also be protected. It is advantageous that the circuit arrangement according to the invention does not require any freewheeling diodes, since the overvoltage protection is connected directly to sensitive semiconductors and works bidirectionally. The electrical circuit arrangement can be combined with soft turn-off and/or a small capacitor in order to reduce voltage peaks which occur due to leakage inductances in the protective circuit and/or in the vicinity of a semiconductor (e.g. drain leakage inductance or parasitic busbar inductance), whereby the capacitor (C) can be dimensioned much smaller than a circuit arrangement that exclusively comprises a snubber, in particular less than 1 µF, the capacitance of the capacitor depending on the parasitic inductance (L _par ). If $$L_{par}>150nH$$

The integration of a capacitor can be particularly useful. Additionally or alternatively, the integration of a capacitor can be useful for 800V systems if L _SYS < 6µH and for 400V systems if L _SYS < 3µH, where L _SYS is integrated into the electrical system through an energy storage device, cables and/or busbars System registered inductance represents.

In addition, the electrical circuit arrangement according to the invention is a redundant system, since no residual current flows through the protective circuit after the semiconductors have been opened, since the same switches can be used in the first switching device and in the second switching device. This means that a single error does not lead to a safety-critical failure of the connected system. It is also advantageous that the residual current of the varistors is lower in the event of a real short circuit due to the voltage drop in the battery during and after the short circuit. The electrical circuit arrangement according to the invention can also be used for applications with low power (e.g. 48 V), in which TVS diodes (transient voltage suppressor and) and/or the avalanche effect of the semiconductor switches are usually used, and develop its advantages in particular when the inductances are very high.

The subclaims show preferred developments of the invention.

The first switching device preferably comprises at least a first switch, in particular a switch with a semiconductor or a plurality of parallel semiconductors. Additionally or alternatively, the first can Switching device includes a second switch, in particular a switch with a semiconductor or several semiconductors connected in parallel. The first switch and the second switch are preferably connected in series. The first switch can have a first blocking direction and the second switch can have a second blocking direction, the second blocking direction preferably being oriented opposite to the first blocking direction. The second switching device preferably comprises at least one third switch, in particular a switch with a semiconductor or several semiconductors connected in parallel. Additionally or alternatively, the second switching device comprises a fourth switch, in particular a switch with a semiconductor or several semiconductors connected in parallel. The third switch and the fourth switch are preferably connected in series. The third switch preferably has a third blocking direction and the fourth switch preferably has a fourth blocking direction, the third blocking direction preferably being oriented opposite to the fourth blocking direction. The first switch and/or the second switch and/or the third switch and/or the fourth switch can preferably be a transistor, preferably a field effect transistor with an insulated gate (IGFET), in particular a metal-oxide semiconductor field effect transistor (English metal-oxide semiconductor field-effect transistor). effect transistor, MOSFET also MOS-FET, rarely MOST). A soft turn-off (STO) can be integrated by, for example, increasing the gate resistance of the MOSFETs. The maximum clamping voltage decreases if the MOSFETs are opened more slowly due to the STO. Additionally or alternatively, the STO can be integrated with accelerated voltage drop to, for example, 9V (two-level turn-off).

The first switch can be, for example, or include a first MOSFET (metal-oxide-semiconductor field effect transistor). Additionally or alternatively, the second switch can be a second MOSFET and/or the third switch can be a third MOSFET and/or the fourth switch can be a fourth MOSFET.

The first varistor and/or the second varistor are preferably metal oxide varistors (MOV).

A first snubber (Boucherot element, RC extinguishing combination, RC spark extinguishing combination, RC extinguishing element) can be connected in parallel to the first overvoltage protection. Additionally or alternatively, a second snubber can be connected in parallel to the second overvoltage protection. A snubber is in particular an electrical circuit that is set up to neutralize unwanted high frequencies or voltage peaks.

The electrical circuit arrangement can be connected to a power supply. To connect the electrical circuit arrangement to the power supply, the electrical circuit arrangement can be equipped with a first terminal and a second terminal for a power supply. The voltage of the power supply is preferably between 48 V and 1kV. The current strength of the power supply is preferably between 10A and 3kA. The inductance introduced by the energy supply is in particular between 2 and 50 pH. The energy supply can be, for example, an energy storage device, in particular a battery (and/or an accumulator). Additionally or alternatively, the energy supply can be an energy network, in particular a 230 V network.

The first overvoltage protection preferably has a predefined first threshold voltage. If the threshold voltage is reached, the varistor preferably conducts a small current. The predefined first threshold voltage is preferably lower than the first breakdown voltage threshold of the first switching device, but in particular lower than the maximum voltage of the battery. The same applies to the second overvoltage protection, which preferably has a predefined second threshold voltage which is lower than the second breakdown voltage threshold of the second switching device, but in particular lower than the maximum voltage of the battery. When dimensioning, it is particularly important to take into account that the maximum clamping requirements (usually lower than the breakdown voltage threshold of the switching device) are met at maximum current (usually short-circuit current).

The maximum short-circuit current can be calculated using the following formula: $$I_{\text{Short circuit}\text{,Max}}=I_{bAT,max}+\left[t_{prOp\left(SCD\right)}+t_{STO\left(beGren\mathrm{e.g}unG\right)}\right]\cdot \frac{v_{bAT}}{L_{bAT}}$$

Therein I mean _BAT,max = maximum battery current; t _prop(SCD) = delay & debounce until short circuit is detected by the hardware circuit, t _{STO(limitation)} = time until semiconductor switch limits the current, V _BAT = battery voltage in the event of a short circuit, L _BAT = system inductance.

The dimensioning should preferably be based on the residual current that occurs. The residual current is usually less than a few pA because the voltage is divided between the first switching device (HSS) and the second switching device (LSS): $$v_{DS\left(xxx\right)}\cong \frac{v_{ba\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="DE102022203310A1\_0005.png"\; state="\{\{state\}\}">t</figure-callout>}}}{2}$$

Since the varistors have a larger residual current in the event of a double fault, which in particular can include, for example, a short circuit and severe aging in one of the overvoltage protection systems and/or which can include, for example, a short circuit in the first switching device and/or a short circuit in the second switching device have to withstand a period of time, the varistors should be designed for a larger residual current, e.g. 10 A. An additional (optional) relay and/or an additional switch only opens after approx. 5ms to 50ms due to the hardware/software control.

The maximum residual current can be found using the voltage-current characteristic curve in the varistor data sheet by looking at the current value at the maximum battery voltage. The tolerance (spread e.g. ±5%, 8%, 10%) of the varistor should also be taken into account.

In addition, when dimensioning the varistors, the maximum residual current should be taken into account when the voltage is steady and the first switching device and/or the second switching device is open, whereby a residual current may flow through the varistors. The varistor is therefore dimensioned such that the threshold voltage of the varistor is below the maximum voltage of the battery. This reduces the voltage peaks when switching off. The resulting residual current is stopped by opening a second and/or third switch. Particularly preferred dimensions are, for example, 400V: 250-MOV; 450V: 275-MOV; 800V: 460-MOV; 900V: 510-MOV.

The elements of the electronic circuit arrangement are preferably applied to a printed circuit board (printed circuit board, PCB). In other words, the circuit board is the carrier of the electronic components and is used for mechanical fastening and electrical connection of the elements.

The electrical circuit arrangement according to the invention can be used, for example, in an electric vehicle, hybrid vehicle, plug-in hybrid vehicle, aircraft, pedelec or e-bike, for portable devices for telecommunications or data processing, for electric hand tools or kitchen machines, as well as in stationary storage for storing, in particular, regeneratively generated electrical Energy can be arranged. In addition, the electrical circuit arrangement according to the invention can be arranged in particular in an electronic battery separation device for HV systems in electromobility and/or in DC (micro) grids and/or DC charging stations. The circuit arrangement can also be arranged, for example, in AC applications.

According to a second aspect of the present invention, an electric vehicle, hybrid vehicle and / or plug-in hybrid vehicle is proposed, which has a device for an overvoltage protection system for a circuit that has a parasitic inductance during a switch-off process according to the first-mentioned aspect of the invention. The device can be arranged permanently and in particular distributed on the electric vehicle, hybrid vehicle and/or plug-in hybrid vehicle. In this way, the features, combinations of features and advantages also arise in a corresponding manner for the electric vehicle, hybrid vehicle and/or plug-in hybrid vehicle.

Short description of the drawing

• 1 eine erfindungsgemäße elektrische Schaltungsanordnung für ein Überspannungsschutzsystem für einen bei einem Abschaltvorgang mit einer parasitären Induktivität behafteten Schaltkreis.

Exemplary embodiments of the invention are described in detail below with reference to the accompanying drawing. In the drawing is:

• 1 an electrical circuit arrangement according to the invention for an overvoltage protection system for a circuit that has a parasitic inductance during a switch-off process.

Preferred embodiment of the invention

1 shows an electrical circuit arrangement according to the invention. The positive pole 12 of a battery 11 is connected to an electrical conductor 9 having parasitic inductances with the first connection 4 of a first switching device 14, which has a first MOSFET 1 and a first MOFSET 1 in Series-connected second MOSFET 2 includes connected. A first varistor 3 is connected parallel to the first switching device 14. The first varistor 3 is dimensioned such that the threshold voltage is below the maximum voltage of the battery 11. The negative pole 13 of the battery 11 is connected to a second connection 8 of a second switching device 15, which comprises a third MOSFET 5 and a fourth MOSFET 6 connected in series with the third MOFSET 5. A second varistor 7 is connected in parallel to the second switching device 15. The second varistor 7 is dimensioned such that the threshold voltage is below the maximum voltage of the battery 11. The first switching device 14 and the second switching device 15 are connected to one another with an electrical conductor 9. There is a system 10 between the first switching device 14 and the second switching device 15. If there is a short circuit in the system 10, the current does not flow via the first switching device 14, but rather via the first varistor 3 and not via the second switching device 15, but rather over the second varistor 4. In this way, the first switching device 14 and the second switching device 15 are protected from the energy during a switch-off operation under load, which is stored in the parasitic inductors.

Alternative and not in 1 shown, all switches 1, 2, 5, 6 or at least one of the switches 1, 2, 5, 6 of the switching devices 14, 15 is a mechanical switch.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102016011815 B3 [0003]
• DE 1811642 B2 [0004]
• DE 2753171 [0005]

Claims (9)

Electrical circuit arrangement for an overvoltage protection system for a circuit which has a parasitic inductance during a switch-off process, the electrical circuit arrangement comprising: - a first switching device (14) with a first connection (4) and a third connection (16), wherein - A first varistor (3) is connected in parallel to the first switching device (14), and - a second switching device (15) with a second connection (8) and a fourth connection (17), wherein - A second varistor (7) is connected in parallel to the second switching device (15), and - The third connection (16) of the first switching device (14) is connected to the fourth connection (17) of the second switching device (15) via an electrical conductor (9). Electrical circuit arrangement according to Claim 1 , wherein the first switching device (14) comprises at least one first switch (1), in particular also a second switch (2) connected in series with the first switch (1), and the second switching device (15) at least one third switch (6), in particular also includes a fourth switch (5) connected in series with the third switch (6). Electrical circuit arrangement according to Claim 2 , wherein the first switch (1) is a first MOSFET and / or the second switch (2) is a second MOSFET and / or the third switch (6) is a third MOSFET and / or the fourth switch (5) is a fourth MOSFET. Electrical circuit arrangement according to Claim 1 until 3 , wherein the first varistor (3) and / or the second varistor (7) is a metal-oxide varistor. Electrical circuit arrangement according to one of the preceding claims, wherein a first snubber is connected in parallel to the first varistor (3) and/or a second snubber is connected in parallel to the second varistor (7). Electrical circuit arrangement according to one of the preceding claims, wherein the electrical circuit arrangement is connected to a power supply, the power supply preferably being a battery (11) with a predefined battery voltage. Electrical circuit arrangement according to one of the preceding claims, wherein the first varistor (3) has a predefined first threshold voltage which is lower than a maximum voltage of the battery (11), and / or the second varistor (7) has a predefined second threshold voltage which is lower is than the maximum voltage of the battery (11). Electrical circuit arrangement according to one of the preceding claims, wherein the electrical circuit arrangement is mounted on a circuit board. Electric vehicle, hybrid vehicle and/or plug-in hybrid vehicle, comprising an electrical circuit arrangement according to one of the preceding claims.

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