WO2019219282A1

WO2019219282A1 - Electrical circuit and method for operating an electrical circuit

Info

Publication number: WO2019219282A1
Application number: PCT/EP2019/057996
Authority: WO
Inventors: Axel Haas; Soeren QUASS
Original assignee: Robert Bosch Gmbh
Priority date: 2018-05-15
Filing date: 2019-03-29
Publication date: 2019-11-21
Also published as: DE102018207491A1

Abstract

The invention relates to an electrical circuit comprising a semiconductor switch, an inductance connected in series with the semiconductor switch, and comprising an overcurrent identification circuit for determining an overcurrent in the electrical circuit, wherein the overcurrent identification circuit has a first comparator circuit configured to detect a control voltage of the semiconductor switch, and a second comparator circuit configured to detect an inductance voltage present at the inductance. Provision is made for the overcurrent identification circuit to have a third comparator circuit configured to detect an integral of the inductance voltage, which integral is taken into account when determining the overcurrent.

Description

description

title

Electric circuit, method for operating an electrical circuit

The invention relates to an electrical circuit having a semiconductor switch, an inductance connected in series with the semiconductor switch, and having an overcurrent detection circuit for detecting an overcurrent in the electrical circuit, wherein the overcurrent detection circuit comprises a first comparator circuit adapted to detect a control voltage of the semiconductor switch , and a second comparator circuit, which is designed to detect an inductance voltage applied to the inductance.

Furthermore, the invention relates to a method for operating the above-mentioned electrical circuit.

State of the art

Electrical circuits of the type mentioned are known from the prior art. According to the so-called "2 D short circuit detection method", an overcurrent is detected by means of an overcurrent detection circuit. For this purpose, the overcurrent detection circuit has a first comparator circuit, which is designed to monitor a control voltage applied to a semiconductor switch of the electrical circuit. In addition, the overcurrent detection circuit has a second comparator circuit, which is designed to monitor an inductance voltage applied to an inductance of the electrical circuit. Depending on the detected control voltage and the detected inductance voltage, an overcurrent in the electrical circuit is determined according to the "2D short-circuit detection method". The inductance voltage is in this case not proportional to the current intensity of the current in the electrical circuit, but to a

Current slew rate, so doubling the

Current slew rate also doubles the

Induced voltage causes. Thus, an overcurrent resulting from a high current slew rate is, for example, in the case of

Short circuit in the electrical circuit, reliably determinable.

Disclosure of the invention

The inventive method with the features of claim 1 has the advantage that also an overcurrent, which consists of a small

Current slew rate results, is reliably determinable. Thus, the accuracy of the overcurrent detection is increased. According to the invention, it is provided that the overcurrent detection circuit has a third

Comparator, which is adapted to an integral of the

Inductance voltage to be detected, the integral is taken into account when determining the overcurrent. In contrast to the inductance voltage itself, the integral of the inductance voltage is proportional to the current intensity in the electrical circuit, so that the overcurrent can be detected independently of the current rise rate of the current.

According to a preferred embodiment, it is provided that the first comparator circuit has a first comparator, which is designed to compare the control voltage with a predefinable first reference voltage, wherein the first comparator circuit is adapted to emit a first overcurrent sub-signal, if the comparison shows that the

Control voltage is greater than the first reference voltage. This results in the advantage that, depending on the elements of the electrical circuit, in particular depending on the semiconductor switch, different first reference voltages are selectable, the exceeding of which is an indication of the presence of the overcurrent in the electrical circuit. In particular, the first reference voltage is chosen such that it is at a normal

Switching operation of the semiconductor switch or during a conductive operation of the semiconductor switch is not exceeded by the control voltage.

Preferably, the reference voltage is above the Miller plateau of Switch-on, so above a temporarily constant

Control voltage following a power-on of the

Semiconductor switch is achieved.

Preferably, the second comparator circuit has a second comparator, which is designed to compare the inductance voltage with a predefinable second reference voltage, wherein the second comparator

Comparator circuit is adapted to emit a second overcurrent sub-signal when the comparison shows that the inductance voltage is greater than the second reference voltage. This results in the advantage that, depending on elements of the electrical circuit, for example, depending on the inductance, different second reference voltages are selectable, the exceeding of which indicates the presence of the

Overcurrent in the electrical circuit is.

According to a preferred embodiment, it is provided that the third comparator circuit has a third comparator, which is designed to compare the integral with a predefinable third reference voltage, wherein the third comparator circuit is configured to a third

Overcurrent signal to send out when the comparison shows that the integral is greater than the third reference voltage. This results in the advantage that, depending on elements of the electrical circuit, for example, depending on the inductance, different third reference voltages can be selected, the exceeding of which indicates the presence of the

Overcurrent in the electrical circuit is.

Preferably, the third comparator circuit for detecting the integral comprises an integrator. As a result, the integral of the inductance voltage is reliable, in particular independently of the rate of current rise, detectable.

It is preferably provided that the integrator is preformed to the third comparator. This has the advantage that the integral detected by the integrator is passed to the third comparator, so that the third comparator can compare the integral with the third reference voltage, as previously described. According to a preferred embodiment it is provided that the

Overcurrent detection circuit comprises an evaluation circuit which is designed to determine the overcurrent in dependence on the overcurrent part signals. Thus, the exceeding of the reference voltages is taken into account when determining the overcurrent. In particular, the overcurrent is determined only in the presence of a combination of overcurrent part signals, in particular of two overcurrent part signals. For example, no overcurrent is determined when only the control voltage, only the inductance voltage or only the integral exceed the respective reference voltage, that is, only the first overcurrent sub-signal, only the second overcurrent sub-signal or only the third overcurrent sub-signal. This reduces the likelihood of false-positive results.

According to a preferred embodiment it is provided that the

Evaluation circuit is designed to, in the presence of the first

Überstromteilsignals on the one hand and in the presence of the second

On the other hand, overcurrent signal and / or the third overcurrent part signal to determine the overcurrent. This results in the advantage that, on the one hand, an overcurrent with a high current slew rate can be determined particularly quickly due to the presence of the first overcurrent part signal and the second overcurrent part signal, and, on the other hand, an overcurrent with a low current slew rate can be reliably determined by the presence of the first overcurrent part signal and the third overcurrent part signal is.

Preferably, the semiconductor switch is a field effect transistor, in particular MOSFET, or a bipolar transistor, in particular IGBT. This results in the advantage that the switching is easy and without high energy consumption.

The inductance is preferably arranged on an inflow side of the semiconductor switch. This results in a particularly simple structure of

Overcurrent detection circuit.

According to a preferred embodiment, the electrical circuit has at least one reference ground for detecting the inductance voltage. This results in the advantage that the inductance voltage is particularly simple, especially on only one side of the inductance, preferably between the inductance and the semiconductor switch, can be measured. Alternatively, a differential measurement of the inductance voltage is provided. The electrical circuit is then designed to detect the inductance voltage on both sides of the inductance.

According to a preferred embodiment it is provided that the electrical circuit is designed to perform at least one safety measure when an overcurrent is detected. This results in the advantage that elements of the electrical circuit and connected to the electrical circuit elements, such as power amplifiers, are protectable from the overcurrent. Preferably, the current flow is interrupted when determining the overcurrent as a safety measure by the electrical circuit. For this purpose, in particular the semiconductor switch and / or another optional existing switch, which is designed to interrupt the current flow, suitably controlled.

The inventive method with the features of claim 13 for operating a particular inventive electrical circuit having a semiconductor switch, an inductor connected in series with the semiconductor switch and an overcurrent detection circuit for detecting an overcurrent, characterized in that a control voltage of the semiconductor switch, a Inductance applied to the inductance and an integral of the inductance voltage are detected, wherein the overcurrent is determined at least in dependence of the integral. This results in the already mentioned advantages.

According to a preferred embodiment, it is provided that at least one safety measure is performed when an overcurrent is detected or detected / detected.

In the following, the invention will be explained in more detail with reference to the drawings. To show: Figure 1 shows an embodiment of an advantageous electrical

Circuit,

2 shows a method for operating the electrical circuit.

1 shows a simplified representation of an embodiment of an advantageous electrical circuit 1. The electrical circuit 1 has a power path 2, in which a semiconductor switch 3, in this case MOSFET, and an inductance 4, in this case a coil, are arranged. According to the exemplary embodiment illustrated in FIG. 1, the inductance 4 is arranged on an inflow side 17 of the semiconductor switch 3. In addition, the electrical

Circuit 1, a half-bridge driver 5, which is adapted to generate a control voltage for switching the semiconductor switch 3, so that when applied control voltage, a current flow through the semiconductor switch 3 is possible.

According to a further exemplary embodiment, the semiconductor switch 3 is designed as a bipolar transistor, in particular as an IGBT. According to this

Embodiment, the half-bridge driver 5 is designed to a

Base current for switching the formed as a bipolar transistor

Semiconductor switch 3 to produce.

According to the exemplary embodiment illustrated in FIG. 1, the electrical circuit 1 has an overcurrent detection circuit 6, shown in dashed lines, for detecting an overcurrent in the electrical circuit 1, whose

Functionality to be described below.

The overcurrent detection circuit 6 has a first comparator circuit 7, a second comparator circuit 8 and a third comparator circuit 9.

The first comparator circuit 7 is designed to be connected to the

Semiconductor switch 3 applied control voltage to capture. For this purpose, the first comparator circuit 7 has a first comparator 10, which is also designed to compare the detected control voltage with a predefinable first reference voltage U_RefA. The first comparator circuit 7 is configured to emit a first overcurrent sub-signal when the

Comparison shows that the control voltage is greater than the first one Reference voltage U_RefA is. In this case, the first reference voltage U_RefA is selected such that it is at least temporarily greater than the control voltage applied to the semiconductor switch 3 during normal operation of the electrical circuit 1, ie in the absence of an overcurrent.

The second comparator circuit 8 is designed to detect an inductance voltage applied to the inductance 4. For this purpose, the second

Comparator 8 a second comparator 11, which is also adapted to the detected inductance voltage with a second

Reference voltage U_RefB to compare. This is the second

Comparator 8 is adapted to emit a second overcurrent sub-signal when the comparison shows that the inductance voltage is greater than the second reference voltage U_RefB.

The third comparator circuit 9 is configured to be an integral of

To detect inductance voltage. For this purpose, the third comparator circuit 9 has an integrator 12. For detecting the integral of the integrator 12 is the input side with the semiconductor switch 3 side facing the

Inductance 4 and a reference ground 18 connected. Accordingly, the inductance 4 on a side facing away from the semiconductor switch 3, a reference ground 19 is assigned. The integrator 12 is followed by a third comparator 13, which is designed to compare the integral of the inductance voltage detected by the integrator 12 with a third reference voltage U_RefC. In this case, the third comparator circuit 9 is configured to emit a third overcurrent sub-signal when the comparison reveals that the integral is greater than the third reference voltage U_RefC.

The comparator circuits 7, 8, 9 is an evaluation circuit 14

downstream. The evaluation circuit 14 has a first

Evaluation subcircuit 15 on the input side with the second

Comparator 8 and the third comparator circuit 9 is connected and adapted to receive the second and / or the third overcurrent sub-signal, and in the presence of one or both of the

Überstromteilignale, the overcurrent sub-signal or the

Forward overcurrent signals. In addition, the evaluation circuit 14, a second evaluation sub-circuit 16 which is adapted to the by the receive first evaluation sub-circuit 15 forwarded overcurrent part signals. The second evaluation sub-circuit 16 is also connected on the input side to the first comparator circuit 7 and configured to receive the first overcurrent sub-signal and in response to the received

Overcurrent signals to determine the overcurrent. In the present case, the second evaluation sub-circuit 16 is designed to be in the presence of the first

Überstromteilsignals on the one hand and in the presence of the second

On the other hand, overcurrent signal and / or the third overcurrent part signal to determine the overcurrent. Thus, according to that shown in FIG

Embodiment of the overcurrent determined when, on the one hand, the

Control voltage is greater than the first reference voltage U_RefA, and if on the other hand, the inductance voltage is greater than the second reference voltage U_RefB and / or the integral is greater than the third reference voltage U_RefC.

According to a further exemplary embodiment (not illustrated here), the second evaluation subcircuit 16 is designed as an alternative or in addition, in the presence of only one overcurrent signal and / or in the presence of another

Combinations of overcurrent signals to determine the overcurrent.

According to the exemplary embodiment illustrated in FIG. 1, the electrical circuit 1 is designed to carry out at least one safety measure when determining the overcurrent. For this purpose, the electrical circuit 1 shown in Figure 1 is adapted to drive the semiconductor switch 3 such that the current flow in the power path 2 is interrupted.

2 shows a flowchart illustrating an exemplary method for operating the electrical circuit 1. In a first step S1, the control voltage applied to the semiconductor switch 3, the inductance voltage applied to the inductance 4 and the integral of the inductance voltage are detected. The detected voltages are compared in a second step S2 with the predetermined reference voltages U_RefA, U_RefB, U_RefC. In this case, it is provided that different reference voltages U_RefA, U_RefB, U_RefC are respectively used for the control voltage, the inductance voltage and for the integral. In a third step S3, at least one overcurrent sub-signal is transmitted if the comparison shows that one of the detected voltages greater than the respective voltage associated reference voltage U_RefA, U_RefB, U_RefC is. It is provided that the first overcurrent sub-signal is emitted when the control voltage is greater than the first reference voltage U_RefA that the second

Overcurrent sub-signal is emitted when the inductance voltage is greater than the second reference voltage U_RefB, and that the third

Overcurrent sub-signal is sent out when the integral is greater than the third reference voltage U_RefC. In a fourth step S4, it is determined whether there is an overcurrent in the electrical circuit 1. For this purpose, the

evaluated overcurrent part signals. According to the embodiment shown in Figure 2, the overcurrent in the presence of the first overcurrent part signal on the one hand and in the presence of the second

Overcurrent part signal and / or the third overcurrent part signal on the other hand determined. When ascertaining the overcurrent in the electrical circuit 1, suitable safety measures are carried out in a fifth step S5. In this case, safety measures are provided which are suitable for protecting elements of the electrical circuit 1 or elements electrically connected to the electrical circuit 1 from overcurrent. For this purpose, for example, the semiconductor switch 3 or other optional switches are controlled such that the current flow in the line path 2 is interrupted.

Claims

claims

1. Electrical circuit (1) with a semiconductor switch (3), one with the

Semiconductor switch (3) inductor (4) connected in series, and with an overcurrent detection circuit (6) for detecting an overcurrent in the electrical circuit (1), the overcurrent detection circuit (6) having a first comparator circuit (7) designed to to detect a control voltage of the semiconductor switch (3), and a second comparator circuit (8) which is adapted to detect an inductance voltage applied to the inductance (4), characterized in that the overcurrent detection circuit (6) has a third

Comparator (9), which is adapted to detect an integral of the inductance voltage, which is taken into account in determining the overcurrent.

2. An electrical circuit according to claim 1, characterized in that the first comparator circuit (7) comprises a first comparator (10) which is adapted to compare the control voltage with a predetermined first reference voltage (U_RefA), wherein the first

Comparator circuit (7) is adapted to emit a first overcurrent sub-signal when the comparison shows that the control voltage is greater than the first reference voltage (U_RefA).

3. Electrical circuit according to one of the preceding claims, characterized in that the second comparator circuit (8) comprises a second comparator (11) which is adapted to compare the inductance voltage with a predetermined second reference voltage (U_RefB), wherein the second comparator circuit (8) is adapted to emit a second overcurrent sub-signal when the comparison reveals that the inductance voltage is greater than the second reference voltage (U_RefB).

4. Electrical circuit according to one of the preceding claims, characterized in that the third comparator circuit (9) has a third comparator (13) which is adapted to compare the integral with a predetermined third reference voltage (U_RefC), wherein the third comparator circuit (9) is designed to a third

Output overcurrent signal when the comparison shows that the integral is greater than the third reference voltage (U_RefC).

5. Electrical circuit according to one of the preceding claims, characterized in that the third comparator circuit (9) for detecting the integral comprises an integrator (12).

6. An electrical circuit according to claim 5, characterized in that the integrator (12) is connected upstream of the third comparator (13).

7. Electrical circuit according to one of claims 4 to 6, characterized

characterized in that the overcurrent detection circuit (6) has a

Evaluation circuit (14) which is designed to determine the overcurrent in dependence on the overcurrent part signals.

8. Electrical circuit according to claim 7, characterized in that the evaluation circuit (14) is adapted to, in the presence of the first overcurrent part signal on the one hand and in the presence of the second

On the other hand, overcurrent signal and / or the third overcurrent part signal to determine the overcurrent.

9. Electrical circuit according to one of the preceding claims, characterized in that the semiconductor switch (3) is a field effect transistor, in particular MOSFET, or a bipolar transistor, in particular IGBT, is.

10. Electrical circuit according to one of the preceding claims, characterized in that the inductance (4) on an inflow side (17) of the semiconductor switch (3) is arranged.

11. Electrical circuit according to one of the preceding claims, characterized in that it comprises at least one reference ground (18, 19) for detecting the inductance voltage.

12. Electrical circuit according to one of the preceding claims, characterized in that it is designed to perform at least determine a safety measure when determining the overcurrent.

13. A method for operating an electrical circuit (1), in particular

according to one of claims 1 to 12, comprising a semiconductor switch (3), an inductor (4) connected in series with the semiconductor switch (3) and an overcurrent detection circuit (6) for detecting an overcurrent, wherein a control voltage of the semiconductor switch (3) and an inductance voltage applied to the inductance (4) is detected, characterized in that an integral of the inductance voltage is detected, and the overcurrent is determined at least as a function of the integral.

14. The method according to claim 13, characterized in that at least one safety measure is performed when an overcurrent is detected.