Patent ID: 12196819

DETAILED DESCRIPTION

FIG.1shows an H-bridge electronic circuit1, arranged in an integrated circuit13.

In the present example, this H-bridge is designed for an automobile application and is powered by the voltage of the battery of a vehicle in order to control a load12. The load12is, for example, an electric motor activating a valve or a flap for controlling the propulsion engine of the vehicle. As a variant, the load12can be formed by any element requiring an H-bridge for the control thereof.

The H-bridge in this case comprises a high potential power supply terminal2, which is connected to the positive terminal of the battery of the vehicle (for example, +12 volts potential), as well as a low potential power supply terminal3, which in this example is connected to the ground of the vehicle.

The H-bridge thus comprises a “high side”4powered by the high potential terminal2, and a “low side”5powered by the low potential terminal3.

The H-bridge comprises two output terminals6,7connected to the terminals of the load12. These output terminals6,7are identified in the present description by the qualifying terms “left terminal”6and “right terminal”7, with reference to the diagram ofFIG.1.

Between each side (high 4 or low5) and the output terminals6,7, the H-bridge comprises four branches each provided with a switch8,9,10,11. In the present example, the switches8,9,10,11are produced by transistors schematically shown inFIG.1by a diode and a switch (the control part of the transistors has not been shown).

In the present example, the H-bridge circuit1is integrated within a specialized integrated circuit13of the ASIC (Application Specific Integrated Circuit) type, which comprises, in addition to the H-bridge, a module14comprising computation means (a microcontroller, for example) adapted to control the switches8,9,10,11and to perform the diagnostics of the H-bridge. The module14also comprises voltage measurement means adapted to measure the potential of each output terminal6,7of the H-bridge.

The H-bridge thus comprises:a high side branch comprising a switch8connected between the high potential terminal2and the left output terminal6;another high side branch comprising a switch9connected between the high potential terminal2and the right output terminal7;a low side branch comprising a switch10connected between the low potential terminal3and the left output terminal6;another low side branch comprising a switch11connected between the low potential terminal3and the right output terminal7.

The module14controls the switches8,9,10,11in a conventional manner for an H-bridge, as a function of the control intended for the load12.

The H-bridge further comprises means for detecting a short-circuit including four current sources15,16,17,18each disposed parallel to a switch8,9,10,11.

In this example:a current source15is disposed parallel to the switch8;a current source16is disposed parallel to the switch9;a current source17is disposed parallel to the switch10;a current source18is disposed parallel to the switch11.

The current sources15to18are each simply schematically shown using the symbol of a current source in series with a switch allowing it to be activated or deactivated.

The module14is adapted to activate a mode for detecting a short-circuit allowing anomalies affecting the H-bridge to be detected. This mode for detecting a short-circuit is based on the use of the current sources15to18and is implemented when stopped, i.e., when the load12is not controlled. This detection mode can be activated, for example, each time the vehicle is turned on, as a start-up routine, or during any other phase when the load12is stopped.

The method for detecting a short-circuit of the H-bridge is described with reference to the diagram ofFIG.2.

The method starts with a step20, in which one of the current sources15to18is activated. To this end, a branch of the H-bridge is initially selected as a first test branch. Any branch of the H-bridge can be the first test branch. In the example described, the branch containing the switch10is selected as the first test branch.

The current source17in this case is therefore activated first, while the other current sources15,16,18remain deactivated.

A subsequent step21involves carrying out a first potential measurement, during which the potential of the output terminal6corresponding to the first test branch is measured. However, the presence of the load12implies that the potentials of the two outputs6,7are equal.

The next step22involves comparing the measured potential of the output terminal6with the potential on the (high or low) side of the first test branch. In this example, with the switch10being connected to the low side5, the potential measured for the output terminal6is compared with the potential of the low potential terminal3, i.e., with the reference potential. If these potentials are substantially different, the method proceeds to step23. For example, if the potential measured during the first potential measurement is located outside the range [−0.5 V; +0.5 V], in this case it is considered to be different from 0 V and the method proceeds to step23. Since the first test branch is on the low side5, the reference potential of 0 V is indeed that which must be obtained during this first potential measurement, if no short-circuit disrupts the H-bridge.

When proceeding to step23, the potential originating from the first potential measurement is, as previously indicated, different from the ground potential, which corresponds to an abnormal value and indicates the presence of a short-circuit that will be more precisely characterized throughout the remainder of the method.

During step23, another branch of the H-bridge is selected as a second test branch. This second test branch is diametrically opposite to the first test branch. In the present example, this is the branch comprising the switch9. The expression “diametrically opposite” used herein describes an element that is located on the other (high or low) side, as well as on the other (right or left) edge, relative to a considered element.

In the example described, the current source16is then activated in addition to the current source17that remains activated, while the other current sources15,18remain deactivated.

A second potential measurement is then taken in step24. The potential of each of the output terminals6,7is measured during this step.

The next step25involves comparing the potential measurements of the two terminals6,7, originating from the second measurement, with the potential originating from the first measurement, and proceeding to step26or to step27according to the following criteria:if the potential of the left output6, which potential is measured during the second potential measurement, is closer to the potential measured during the first potential measurement than the potential of the right output7, which potential is measured during the second potential measurement, then the method proceeds to step26;if the potential of the right output7, which potential is measured during the second potential measurement, is closer to the potential measured during the first potential measurement than the potential of the left output6, which potential is measured during the second potential measurement, then the method proceeds to step27.

Steps26and27relate to the location of the short-circuit, i.e., the short-circuit that was identified in step23will now be located: it can be located in the conductors that are connected to the left output terminal6or in the conductors that are connected to the right output terminal7.

When the method reaches step26this means that the short-circuit affects the left output6of the H-bridge. Step26then involves signalling the detection of a short-circuit in this left output6. This signalling can be carried out using any suitable means as a function of the application, for example, by activating a flag on the module14that is designed to be read and taken into account by corrective or remedial devices of the vehicle (devices that are known and are not described herein).

When the method reaches step27this means that the short-circuit affects the right output7of the H-bridge. Step27then involves signalling the detection of this short-circuit in the left output6, as previously, for example, by activating a flag.

In other words, proceeding to steps26or27occurs by detecting the output terminal6,7having the potential resulting from the second potential measurement that is closest to the potential that was measured during the first potential measurement.

In the particular case of this embodiment:during step26, the potential of the left output6is equal to the potential originating from the first potential measurement, while the potential of the right output7is different from the potential originating from the first potential measurement;during step27, the potential of the left output6is different from the potential originating from the first potential measurement, while the potential of the right output7is equal to the potential originating from the first potential measurement.

The short-circuit indication of steps26,27, respectively, corresponds to a situation where:a short-circuit is present in the cables of the vehicle that are connected to the left output terminal6, and to the right output terminal7, respectively;this short-circuit has a resulting value that is equal to the potential measured during the first potential measurement, i.e., the short-circuited cables have potentials leading to this resulting value, when they are short-circuited. The resulting value of the short-circuit thus assists in identifying the cables involved in the short-circuit.

Indeed, if, for example, the resulting value of the short-circuit is a potential of +12 V, this means that the output conductor connected to the output terminal involved has directly short-circuited with a conductor connected to the positive terminal of the battery of the vehicle. According to another example, if the resulting value of the short-circuit is a potential of −1 V, this means that the output conductor connected to the output terminal involved is short-circuited with a conductor having a potential that is less than the reference potential of the circuit.

Thus, the method allows short-circuits to be identified and located even outside the conventional range of 0 V to 12 V, which is increasingly required in the automobile field in a context involving increasing complexity where many circuits can have different reference potentials, and where the bodywork of a vehicle, taken as ground, can have different potentials in remote regions.

The method thus can comprise an additional step of determining the physical position of the short-circuit on the basis of the identification of the output terminal in which the short-circuit is located and of said resulting value of the short-circuit, i.e., a step of identifying the wiring harness of the vehicle that is connected to the output terminal involved and that comprises the cables likely to produce a short-circuit with such a resulting value. As a variant, the current sources can have different bias voltages between them, in order to facilitate identification.

Furthermore, in contrast with the previous description, if, during step22, the potential of the output terminal6measured during the first potential measurement is substantially equal to the potential of the low potential terminal3, the method then proceeds to step28. In this example, if the potential measured during the first potential measurement is located in the range [−0.5 V; +0.5 V], the method proceeds to step28.

Proceeding to step28corresponds to the normal case of the absence of a short-circuit, which results in a potential of the output terminal6that suitably converges toward the reference potential, with the first test branch being a low side branch5. However, an ambiguity can be created by a short-circuit precisely returning the output terminal6to the reference potential, independently of whether or not the current source17is activated.

In order to increase the precision of the method by removing this ambiguity, it is possible, during step28, to select a branch of the H-bridge as a test branch (it will be called “third test branch” hereafter), with this branch being adjacent to the first test branch (i.e., the same edge, left or right), and being opposite to the first test branch (i.e., on the opposite side, high or low).

In the present example, the branch containing the switch8is selected as a third test branch (this third test branch is on the high side, while the first test branch was on the low side, with these branches both being on the same left edge). During step28, the current source15is then activated while the other current sources16,17,18remain deactivated.

A subsequent step29involves taking a potential measurement (which is called “third potential measurement” in order to identify it relative to the other potential measurements of the method). This third potential measurement involves measuring the potential of the output terminal6corresponding to the third test branch. As in step21, the presence of the load12nevertheless implies that the potentials of the two outputs6,7are equal.

The next step30involves comparing the potential measured during the third potential measurement with the potential corresponding to the side of the first test branch. In this example, with the first test branch (switch10) being on the low side, the potential measured at the output terminal6is compared with the potential of the low potential terminal3, i.e., with the reference potential 0 V. If these potentials are substantially different, the method proceeds to step31. For example, if the potential measured during the third potential measurement is greater than 0.5 V, it is considered in this case that it is substantially different from 0 V and the method proceeds to step36. The potential of 0 V is indeed that which will be obtained during the third potential measurement if a short-circuit specifically disrupts the H-bridge so that the output terminals6,7are constantly at the potential 0 V. When the potential originating from the third potential measurement is thus different from the low potential 0 (and is a priori equal to +12 V), this means that this specific short-circuit is not present, and that the previously mentioned ambiguity is high. In this case, the method then proceeds to the final step of the method, step36, with no short-circuit having been detected.

Furthermore, if, during step30, the potential measured during the third potential measurement is equal to the potential corresponding to the side of the first test branch (0 V in this example), this means that the detection of step22must not conclude that there is no short-circuit since it is actually a short-circuit artificially returning the potential of the output terminals6,7as 0 V that is responsible for this behavior.

Proceeding to step31corresponds to detecting a short-circuit in either one of the output terminals6,7, with this short-circuit having a potential of 0 V as the resulting value. The following steps allow this short-circuit to be located.

During step31, another branch of the H-bridge is selected as a fourth test branch. This fourth test branch is diametrically opposite to the third test branch. In the present example, this is the branch comprising the switch11.

In the example described, the current source18of the fourth test branch is therefore in turn activated, in addition to the current source15, which also remains activated, while the other current sources16,17remain deactivated.

A fourth potential measurement is then taken during step32, with this measurement involving measuring the potential of each of the output terminals6,7.

The next step33involves comparing the potential measurements of the two terminals6,7originating from the fourth potential measurement, with the potential originating from the third potential measurement (which is equal to the potential originating from the first potential measurement, 0 V in the present example), and proceeding to step34or to step35according to the following criteria:if the potential of the left output6, which potential is measured during the fourth potential measurement, is further from the potential measured during the third potential measurement than the potential of the right output7, which potential is measured during the fourth potential measurement, then the method proceeds to step34;if the potential of the right output7, which potential is measured during the fourth potential measurement, is further from the potential measured during the third potential measurement than the potential of the left output6, which potential is measured during the fourth potential measurement, then the method proceeds to step35.

When the method reaches step34this means that the short-circuit affects the left output6of the H-bridge. Step34then involves indicating the detection of a short-circuit in this left output6, for example, by activating a flag as previously.

When the method reaches step35this means that the short-circuit affects the right output7of the H-bridge. Step35then involves indicating the detection of this short-circuit in this left output7, for example, by activating a flag as previously.

In other words, the transition to steps34or35is carried out by detecting the output terminal6,7having the potential resulting from the fourth potential measurement that is furthest from the potential of the first and third potential measurements (0 V in this example).

In the particular case of this embodiment:during step34, the potential of the right output7is equal to the potential originating from the third potential measurement, and is substantially zero, while the potential of the left output6differs from zero;during step35, the potential of the right output7differs from zero, while the potential of the left output6is substantially equal to zero.

The short-circuit indication of steps34,35, respectively, corresponds to a situation where:a short-circuit is present in the cables of the vehicle that are connected to the left output terminal6and to the right output terminal7, respectively;this short-circuit has a resulting value that is equal to zero, i.e., the short-circuited cables have potentials leading to a zero potential, when they are short-circuited. The resulting value of the short-circuit thus assists in identifying the cables involved in the short-circuit, i.e., in this example, the cables connected to the reference potential that are in contact with cables connected to the output terminal involved.

As previously, the method can thus comprise an additional step of determining the physical position of the short-circuit on the basis of the identification of the output terminal in which the short-circuit is located and of said resulting value of the short-circuit, i.e., a step of identifying the wiring harness of the vehicle that is connected to the output terminal involved and that comprises the cables at 0 V that are likely to produce a short-circuit with such a resulting value of 0 V. Also as a variant, the current sources can have different bias voltages between them, in order to facilitate the identification.

The method thus allows a short-circuit to be detected, the potential resulting from the short-circuit to be provided, and the output terminal6,7and the conductors involved to be indicated.

The diagnostic method can start with any of the current sources15to18, other than that provided herein, by way of an example as first and third test branches, as long as the sequence proceeds as described. Thus, when no short-circuit is detected, the potentials of the left6and right7output terminals will be measured at 12 volts when the current sources15and16are activated, while these two potentials will be measured at 0 volts (reference potential) when activating the low side5current sources17,18. In addition, activating two diametrically opposite current sources makes it possible to determine whether the resulting potential increases or decreases, which allows the (left or right) edge of the short-circuit to be determined.

Furthermore, the H-bridge can be integrated within a larger bridge structure, comprising additional switching branches.