DE102022207473B4 - Transient protection - Google Patents

Abstract

Electrical circuit (1) for protecting electrical components from transients, with - at least three lines (3, 4, 5) which electrically connect at least two voltage sources (11, 13) to at least one consumer (21, 22, 23), in particular a load, - at least three first suppressor diodes (6, 7, 8), - and with a second suppressor diode (9) which has a ground reference (10), - wherein each line (3, 4, 5) is electrically connected to one of the first suppressor diodes (6, 7, 8) and the first suppressor diodes (6, 7, 8) are connected to the second suppressor diode (9) via a star point (2) and only cathodes of the suppressor diodes (6, 7, 8, 9) are present in the star point (2), wherein the at least one third line (5) connects the second voltage source, designed as a signal source (13), to a third Consumer (23) electrically connects.

Description

FIELD OF INVENTION

The present invention relates to an electrical circuit for protecting electrical components from transients.

It is known to connect lines in an on-board network with suppressor diodes to protect the loads connected to the lines from transients. Each line is electrically connected to a suppressor diode, which is then each connected to ground.

US 5 493 469 A shows an electrical circuit for protecting electrical components from transients with at least two lines that electrically connect at least one voltage source to at least one consumer, at least two first suppressor diodes, and with a second suppressor diode that has a ground reference, wherein each line is electrically connected to a first suppressor diode and the first suppressor diodes are connected to the second suppressor diode via a star point and only cathodes of the suppressor diodes are present in the star point.

SUMMARY OF THE INVENTION

To improve known circuits, a circuit according to claim 1 is provided.

The on-board network refers to all electrical components in vehicles such as cars, aircraft, ships and trains. The on-board network ensures the power supply and the flow of information between components and control units. Hybrid vehicles often have a high-voltage on-board network and a low-voltage on-board network.

A series connection or parallel connection is the connection of two or more components in a circuit in such a way that they form a single current path. Two components are therefore connected in series if their connection does not have a branch. The number of elements connected in series is arbitrary.

A star connection is the interconnection of any number of connections via a resistor (here: suppressor diode) to a common point, which is called the star point.

A diode is an electronic component that allows current to pass in one direction and blocks the flow of current in the other direction. This is why we talk about forward direction and reverse direction.

Suppressor diodes, also known as transient voltage suppressors (TVS), are diodes used to protect electrical components, e.g. circuits, from short-term voltage pulses. Such voltage pulses can occur in cables connected to the circuit due to switching operations in the network or nearby lightning strikes. The voltage reached for a short time can be sufficient to destroy semiconductor components in the circuit.

Suppressor diodes become conductive when a component-specific voltage threshold is exceeded. The current of the pulse is guided past the component to be protected by a parallel connection and discharged via the reference ground. This means that no destructive voltage can build up above the breakdown voltage of the suppressor. In normal operation, this diode behaves neutrally, apart from a small leakage current and additional capacitance.

Transient voltages (events) are not predictable in terms of time (random) and of limited duration. They do not repeat periodically and their form cannot be clearly predicted. Transients often become visible through lightning or arcs. Transient voltages can arise in the on-board network of a vehicle, for example, through the electrical behavior of other consumers, e.g. through the switching of inductive loads.

In circuits, transients are voltage spikes that can potentially damage the circuit.

If two components with opposite polarity (e.g. diodes) are connected in series, this is also called an anti-serial circuit.

A metal-oxide-semiconductor field-effect transistor (MOSFET) is a type of transistor that belongs to the insulated gate field-effect transistors (IGFET). One MOSFET variant comprises a layer stack made up of a metallic gate electrode, a semiconductor and an oxide dielectric in between. Another MOSFET variant comprises doped polysilicon instead of a metallic gate.

In the case of reverse polarity, the power supply to an electrical component is not polarized according to standard. This is the case, for example, if the two terminals of a battery are swapped. The term usually refers to direct current, since a mix-up here could result in a current Reversal of polarity can also occur due to transients.

Reverse polarity protection prevents destructive current flow in the DC voltage supply if the negative and positive poles are swapped.

A consumer, especially a load, is a device or assembly that is to be protected from transients. In the circuit diagram, it is shown like a resistance component with a rectangle and is usually referred to as 'R' without a subscript, which stands for any unspecified load. As the counterpart to the current source, the electronic load is a current sink.

When we refer to "the first suppressor diode" below, we are describing the basic function. The electrical circuit always has at least two first suppressor diodes and one second suppressor diode.

The basic idea of the invention is transient protection of an electrical component by means of a plurality of first suppressor diodes, wherein each line in which transients are to be prevented has a first suppressor diode. Furthermore, the first suppressor diodes are connected to the second suppressor diode via a star point. Preferably, the first suppressor diodes are connected anti-serially in series with the second suppressor diode, wherein the second suppressor diode has a reference to ground.

The combination of the first and second suppressor diodes protects components of the line from overvoltages with positive polarity, i.e. plus, by making the first suppressor diode conductive in the forward direction and the second suppressor diode conductive in the breakdown direction as soon as the diode-specific forward voltage or breakdown voltage is exceeded. The voltage between the respective line and ground is thus limited to the sum of the forward voltage of the first suppressor diode and the breakdown voltage of the second suppressor diode.
In the case of overvoltages with negative polarity, i.e. minus, the first suppressor diode operates in breakdown and the second suppressor diode operates in forward direction.

In addition, at least a third line is provided for connecting a signal source to a second consumer. If the first and second lines are arranged or designed as a load line, a further line can be provided as a signal line.

Advantageously, the magnitude of the breakdown voltage of the first and second suppressor diodes can be different. This means that positive and negative transients from the vehicle electrical system can be clamped to different voltage levels. This enables the clamping voltages to be easily adapted to the respective vehicle electrical system requirements (12V, 24V, 48V).

Alternatively, the magnitude of the breakdown voltage of the first and second suppressor diodes may be the same.

Advantageous embodiments and further developments emerge from the further subclaims and from the description with reference to the figures of the drawing.

According to a preferred development of the invention, at least one consumer of a line is protected by means of reverse polarity protection. The electrical component, i.e. the load of the line, is thus also protected against reverse polarity with a polarity that is the opposite of the supply voltage.

It is also advantageous if the reverse polarity protection is designed as a MOSFET. This provides reverse polarity protection that has a small voltage drop and therefore low loss values in the normal operating state of the circuit.

It is also advantageous, particularly with capacitive loads on the lines (such as half bridges, H bridges, B6 bridges or power supplies), if the drain-source breakdown voltage of the reverse polarity protection MOSFET is greater than the sum of the negative breakdown voltage of the transient protection and the maximum, nominal vehicle electrical system voltage, i.e. without taking transients into account. This means that the capacitive loads remain charged when negative transients occur, which has a beneficial effect on the availability of diagnostic functions, for example. At the same time, the reverse polarity protection MOSFET and capacitors are subjected to less electrical load because the charge remains on the capacitors and is not discharged into the supply line via the reverse polarity protection MOSFET.

Alternatively, additional reverse polarity protection for a cable can also be designed as a diode. This ensures particularly cost-effective reverse polarity protection.

Preferably, the lines of the electrical circuit can only have diodes as reverse polarity protection. Not every line has to have reverse polarity protection. In particular, a line can be connected to an intermediate circuit capacitor.

It is understood that it can be provided that, depending on the expected power or a tolerable voltage drop in the line during normal operation, a suitable reverse polarity protection is selected, ie a choice is made between a diode and a MOSFET. Different reverse polarity protections can therefore be selected for different lines. It can prove advantageous to select a MOSFET for higher supply currents and a diode for lower supply currents.

According to a preferred development of the invention, a second load (of a second line) ensures at least partial redundancy of a first load (of a first line). The redundant loads are thus protected from transients by means of an identical circuit. This has a cost-saving effect on the electrical circuit.

It is also advantageous if the reverse polarity protection of the first load is designed as a MOSFET and the reverse polarity protection of the second load is designed as a diode.

This is advantageous, for example, if the second load represents a partial redundancy of the first load and it is therefore to be expected that the supply current in the normal operating case of the second line is lower than the supply current of the first line.

In particular, the first line and the second line can be designed and/or arranged as power lines. Their consumers are preferably designed as loads. It goes without saying that the electrical circuit can in principle have any number of power lines. In this case, the voltage source for the first and second lines is not a signal source.

Alternatively, the first line and/or the second line can be designed and/or arranged as signal lines. Their consumers are then preferably designed as signal receivers or signal transmitters. Signal lines are to be connected to a signal source, whereby the signal source can be designed as a voltage source. However, it does not provide a load voltage but rather a signal voltage.

• - wenigstens drei elektrischen Leitungen,
• - wenigstens zwei Abnehmern, wobei
• - die elektrischen Leitungen mit jeweils einem Abnehmer verbunden sind, und wobei
• - die elektrischen Leitungen mit jeweils einer ersten Suppressordiode elektrisch verbunden sind,
• - und das Steuergerät eine zweite Suppressordiode mit einem Massebezug aufweist, und

die ersten Suppressordioden über einen Sternpunkt mit der zweiten Suppressordiode verbunden sind und in dem Sternpunkt ausschließlich Kathoden der Suppressordioden anliegen, wobei die wenigstens eine dritte Leitung eine Signalquelle mit einem zweiten Abnehmer elektrisch verbindet.The invention also relates to an electrical control device for a motor vehicle with

• - at least three electrical cables,
• - at least two customers, whereby
• - the electrical cables are each connected to a consumer, and
• - the electrical lines are each electrically connected to a first suppressor diode,
• - and the control unit has a second suppressor diode with a ground reference, and

the first suppressor diodes are connected to the second suppressor diode via a star point and only cathodes of the suppressor diodes are present at the star point, wherein the at least one third line electrically connects a signal source to a second receiver.

The statements made with regard to the electrical circuit also apply to the control unit. In particular, the control unit can be part of the electrical circuit as described. Voltage and signal sources are usually not part of the control unit. The rest of the electrical circuit described can be arranged in the control unit.

Furthermore, the lines in the control unit can be arranged as power lines, and one or more signal lines can also be present, wherein the power lines and the signal line are connected at the star point.

It is understood that an on-board network for a motor vehicle with electrical lines that are part of an electrical circuit as described above, a first voltage source and a plurality of loads, wherein the voltage source and the loads are connected by means of the electrical circuit, wherein the voltage source, in particular, provides a voltage of 12V or 24V.

It is understood that further on-board networks can be provided, the electrical lines of which are also protected by an electrical circuit as described above, with the on-board networks sharing the circuit.

Accordingly, there is also provided a combined on-board network with an electrical circuit as described above, a first on-board network as described above, and a second on-board network which provides a second voltage source which provides a voltage which differs from the voltage of the first voltage source, wherein the electrical circuit has power lines which are assigned to the first on-board network and signal lines which are assigned to the second on-board network, and the power line and the signal line are connected at the star point.

In addition, the invention relates to a motor vehicle with at least one voltage source and/or the signal source, an electrical circuit and/or an electrical control unit. The motor vehicle is characterized in that the electrical circuit and/or the electrical control unit are designed as described. The motor vehicle has at least one voltage source or one signal source. However, it can advantageously also have a voltage source and a signal source or more than one of the respective sources.

As already described, the signal source can be designed as a voltage source, but is not referred to as such in the present invention. It differs from a voltage source in that a voltage source outputs a load voltage and a signal source outputs a signal voltage.

TABLE OF CONTENTS OF DRAWINGS

• 1 ein schematisches Blockdiagramm einer elektrischen Schaltung gemäß einer Ausführungsform der Erfindung.

The present invention is explained in more detail below with reference to the embodiments shown in the schematic figures of the drawings. They show:

• 1 a schematic block diagram of an electrical circuit according to an embodiment of the invention.

The accompanying drawings are intended to provide a further understanding of embodiments of the invention. They illustrate embodiments and, in conjunction with the description, serve to explain principles and concepts of the invention. Other embodiments and many of the noted advantages will be apparent upon reference to the drawings. The elements of the drawings are not necessarily shown to scale with respect to one another.

In the figures of the drawings, identical, functionally identical and acting elements, features and components are provided with the same reference symbols, unless stated otherwise.

DESCRIPTION OF EXAMPLES OF IMPLEMENTATION

1 shows a block diagram of an electrical circuit 1 according to an embodiment of the invention.

The electrical circuit 1 comprises three lines 3, 4, 5, which connect loads 21, 22, 23 to a voltage source each. The load 21 is connected to a battery 11 via the first line 3. The second load 22 is connected to the battery 11 via the second line 4. The third load 23 is connected to an ignition 13 via the third line 5. The loads 21, 22, 23 are each designed as a circuit, with the load 22 ensuring partial redundancy to the load 21.

In order to protect the loads 21, 22, 23 from transients, the loads 21, 22, 23 are connected in parallel with suppressor diodes 6, 7, 8, i.e. the load 21 is connected in parallel with the suppressor diode 8, the load 22 is connected in parallel with the suppressor diode 7 and the load 23 is connected in parallel with the suppressor diode 6. The suppressor diodes 6, 7, 8 are also connected in series with another anti-serial suppressor diode 9. The suppressor diodes 6, 7, 8, 9 are accordingly connected in the star point 2 and have a ground reference 10.

The line 3 also has a reverse polarity protection 15, which is designed as a diode, and a capacitor 17. The second line 4 also has a reverse polarity protection 16 designed as a diode. A diode can also be arranged on the signal line 5 as reverse polarity protection.

The loads 21, 22, 23, the suppressor diodes 6, 7, 8 and 9 as well as the reverse polarity protections 15 and 16 are arranged in a control unit 24. After installation in a motor vehicle, this is connected to the voltage source 11 and/or the signal source 13 via connections not shown and thus connected to the on-board network of the motor vehicle.

Reference symbols

1

electrical circuit

3

Line

4

Line

5

Line

6

Suppressor diode

7

Suppressor diode

8

Suppressor diode

9

Suppressor diode

2

Star point

10

Mass reference

11

Voltage source

13

Voltage source

15

Reverse polarity protection

16

Reverse polarity protection

17

capacitor

21

load

22

load

23

load

24

electrical control unit

Claims (10)

Electrical circuit (1) for protecting electrical components from transients with - at least three lines (3, 4, 5) that electrically connect at least two voltage sources (11, 13) to at least one consumer (21, 22, 23), in particular a load, - at least three first suppressor diodes (6, 7, 8), - and with a second suppressor diode (9) that has a ground reference (10), - wherein each line (3, 4, 5) is electrically connected to one of the first suppressor diodes (6, 7, 8) and the first suppressor diodes (6, 7, 8) are connected to the second suppressor diode (9) via a star point (2) and only cathodes of the suppressor diodes (6, 7, 8, 9) are present in the star point (2), wherein the at least one third line (5) is the second voltage source, designed as a signal source (13), electrically connects to a third consumer (23). Electrical circuit (1) according to Claim 1 , wherein at least one of the consumers (21, 22, 23), in particular all consumers (21, 22, 23) of the electrical circuit (1), is protected against polarity reversal by means of a polarity reversal protection (15, 16). Electrical circuit (1) according to Claim 2 , wherein the polarity reversal protection (15) is designed as a MOSFET. Electrical circuit (1) according to Claim 2 or 3 , wherein the reverse polarity protection (16) is designed as a diode. Electrical circuit (1) according to one of the preceding claims, wherein a second consumer (22), which is designed as a second load, ensures at least partial redundancy of a first consumer (21), which is designed as a first load. Electrical circuit (1) according to one of the Claims 2 until 5 , wherein the polarity reversal protection (15) of the first consumer (21) is designed as a MOSFET. Electrical circuit (1) according to one of the Claims 2 until 6 , wherein the polarity reversal protection (16) of the second consumer (22) and/or that of the third consumer (23) is designed as a diode. Electrical control device (24) for a motor vehicle with at least three electrical lines (3, 4, 5), the at least two voltage sources (11, 13) are electrically connected to at least one consumer (21, 22, 23), in particular a load, - and with - several consumers (21, 22), - wherein the electrical lines (3, 4, 5) are each electrically connected to a first suppressor diode (6, 7, 8), - and the control device has a second suppressor diode (9) with a ground reference (10), and the first suppressor diodes (6, 7, 8) are connected to the second suppressor diode (9) via a star point (2) and only cathodes of the suppressor diodes (6, 7, 8, 9) are present in the star point (2), wherein the at least one third line (5) is the second voltage source, designed as a signal source (13) electrically connects to a third consumer (23). Electrical control unit (24) according to Claim 8 - wherein the lines (3, 4) are arranged as power lines, and one or more signal lines (5) are present, and the power line (3, 4) and the signal line (5) are connected at the star point (2). Motor vehicle with at least two voltage sources (11, 13), an electrical circuit (1) and/or an electrical control device (24), characterized in that the electrical circuit (1) is designed according to one of the Claims 1 until 7 and/or the electrical control device (24) according to one of the Claims 8 until 9 is formed, wherein the motor vehicle has the signal source (13) which is connected to the signal line (5).

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