Voltage converter including a protection device

Abstract

The present invention provides a converter comprising at least one switching arm (16) including: a ground terminal (17), a power supply terminal (18), a first and second power component (Q1, Q2), and a phase terminal (19). The voltage converter (15) further includes a protection device (22) for the switching arm (16) configured to detect a failure mode in which the first and second power components (Q1, Q2) are in the conducting state. The protection device (22) includes a measuring module (23) arranged to output an offset voltage from a measuring voltage of the switching arm and a reference voltage, and a detection module (24) arranged to output an integral signal corresponding to the integral of the offset voltage. Figure for the abstract: Fig. 2

Description

Title of the invention: Voltage converter comprising a protection device

[0001] The invention relates in particular to a voltage converter, in particular for a rotating electrical machine or for a direct-direct voltage converter. The voltage converter comprises a protection device for detecting a failure of one of the power components of the switching arm and its protection method.

[0002] The invention finds a particularly advantageous application in the field of rotating electrical machines such as alternators, alternator-starters or even reversible machines or electric motors. It is recalled that a reversible machine is a rotating electrical machine capable of working reversibly, on the one hand, as an electric generator in alternator function and, on the other hand, as an electric motor for example to start the thermal engine of the vehicle such as a motor vehicle.

[0003] The vehicle's on-board electrical network is used to power the various electrical equipment of the vehicle. An electrical supply from the electrical network is provided by at least one battery, which can be recharged by a rotating electrical machine.

[0004] A rotating electrical machine comprises a voltage converter, a rotor rotating about an axis and a fixed stator. In alternator mode, when the rotor is rotating, it induces a magnetic field in the stator which transforms it into direct electric current via the voltage converter in order to supply the electrical consumers of the vehicle and recharge the battery. In motor mode, the stator is electrically supplied via the voltage converter which functions as an inverter and induces a magnetic field driving the rotor in rotation for example to start the thermal engine.

[0005] The voltage converter comprises a switching arm for each phase of the stator of the machine or for each winding of a transformer. Each switching arm comprises two electrical power components such as transistors. In the event of failure of at least one of the electrical power components of the switching arm, the electrical currents flowing in said switching arm can quickly damage the non-failing components and damage the electrical network and in particular discharge the battery.

[0006] There are various protection circuits for detecting a failure of one of the electrical power components, in particular by measuring the voltage at the terminals of the component to be protected. These methods preferentially use control chips. However, these control chips may not have sufficient accuracy, a sufficient detection threshold, or sufficient detection speed to effectively protect the component. In addition, these chips are generally expensive and difficult to position in the limited space of the voltage converter.

[0007] The present invention aims to avoid the drawbacks of the prior art by proposing a means of detecting a failure of the switching arm which is effective and easy to implement.

[0008] To this end, the present invention therefore relates to a voltage converter intended to be electrically connected to an electrical network, the voltage converter comprising at least one switching arm comprising a ground terminal intended to be electrically connected to an electrical ground of the electrical network, a power supply terminal intended to be electrically connected to a positive terminal of the electrical network, a first and a second power component each operating as a switch arranged to switch between a blocked state and a conducting state, the power components being arranged in series with respect to each other between the ground terminal and the power supply terminal, a phase terminal arranged between the first power component and the second power component and being intended to be electrically connected to an electrical winding.According to the present invention, the voltage converter further comprises a switching arm protection device configured to detect a failure mode in which the first and second power components are in the on state, the protection device comprising a measurement module arranged to output an offset voltage from a switching arm measurement voltage and a reference voltage and a detection module arranged to output an integral signal corresponding to the integral of the offset voltage.

[0009] The term "on state" means that the power component allows the flow of an electric current, as opposed to "off state" where the current does not flow through said component. This may be a state in which the power component is functional and is controlled by a control module of the voltage converter to be active or a state in which the power component has a fault.

[0010] By performing the integral of a difference between the voltage measured at a point of the switching arm and a reference voltage, the invention makes it possible to detect a failure of one of the power components in an efficient, rapid, reliable, space-saving and inexpensive manner.

[0011] According to one embodiment, the protection device is arranged to detect a situation in which one of the power components is in a passing state due to a failure and the other component is in a passing state due to its operation.

[0012] According to one embodiment, the measuring voltage of the switching arm is measured at the ground terminal or at the power supply terminal of the switching arm. This makes it possible to detect a failure at the switching arm and no longer at the power component itself. This makes it possible to reduce the size of the protection device.

[0013] According to one embodiment, the measurement voltage is measured at the terminals of an electrical component or measured at a point on an electrical trace. This makes it possible to simplify the measurement of the voltage.

[0014] According to one embodiment, the reference voltage corresponds to a signal of the same nature, and in particular cleaner, than the measurement voltage. For example, when the measurement voltage is measured at the ground terminal, the reference voltage is a ground voltage measured at a location other than the measurement voltage. Still for example, when the measurement voltage is measured at the power supply terminal, the reference voltage is a power supply voltage measured at a location other than the measurement voltage.

[0015] According to one embodiment, the reference voltage is measured at a positive input / output terminal of the voltage converter or a ground terminal of the voltage converter.

[0016] According to one embodiment, the reference voltage is a voltage measured outside a switching zone. The switching zone is formed by a power module carrying the switching arm and / or by a capacitance module carrying at least one filtering capacitor. This makes it possible to have a cleaner signal without a parasitic component.

[0017] According to one embodiment, the measuring module comprises a resistor and an inductor arranged in series. This makes it possible to determine the offset voltage in a simple manner.

[0018] According to one embodiment, the measurement module comprises a filtering capacity.

[0019] According to one embodiment, the detection module comprises a capacitor arranged between a ground potential and an output terminal of the detection module, a first resistor arranged between an input terminal of the detection module and said output terminal and a second resistor arranged between a ground potential and the output terminal of the detection module. The association between the capacitance and the two resistors makes it possible to determine the slope of the integral signal of the offset voltage. In addition, the two resistors make it possible to determine an offset of the integral signal to prevent said signal from reaching a negative value which could damage the comparison module.

[0020] According to one embodiment, the detection module further comprises a Zener diode arranged between the input terminal and the first resistor. This improves the accuracy of the integral signal.

[0021] According to one embodiment, the detection module further comprises a third resistor arranged between the capacitance and the first resistor and the second resistor. This makes it possible to give a delay to the integral signal which makes it possible to avoid false detections by the comparison module.

[0022] According to one embodiment, the detection module further comprises a protection diode arranged between the first resistor and the input terminal.

[0023] According to one embodiment, the protection device further comprises a comparison module arranged to emit a comparison signal making it possible to determine whether the integral signal is greater than a threshold value. For example, the comparison signal is active when the integral signal is greater than the threshold value.

[0024] According to one embodiment, the comparison module comprises a comparator.

[0025] According to one embodiment, the protection device further comprises a module of memory arranged to emit an error signal when the failure mode is detected.

[0026] According to one embodiment, the first and second power components are transistors, in particular of the MOSFET type (English acronym for “Metal Oxide Semi-conductor Field Effect Transistor”), metal-oxide-semiconductor structure.

[0027] In one embodiment, the switching arm includes a filtering capacitor electrically connected between the power supply terminal and the ground terminal.

[0028] The present invention also relates to a rotating electrical machine comprising a voltage converter as described above. The rotating electrical machine can, advantageously, form an alternator, an alternator-starter, a reversible machine or an electric motor.

[0029] According to one embodiment, the rotating electrical machine comprises a stator comprising an electrical winding forming several phases, each phase being electrically connected to a switching arm via the phase terminal.

[0030] The voltage converter can also form a DC-DC voltage converter (from the English "Direct Current / Direct Current"), called a direct-direct voltage converter.

[0031] The present invention also relates to a method for protecting a switching arm of a voltage converter as described above intended to be electrically connected to an electrical network, the switching arm comprising: a ground terminal intended to be electrically connected to an electrical ground of the electrical network, a power supply terminal intended to be electrically connected to a positive terminal of the electrical network, a first and a second component of power components each operating as a switch arranged to switch between an off state and an on state, the power components being arranged in series with each other between the ground terminal and the power supply terminal, a phase terminal arranged between the first power component and the second power component and being intended to be electrically connected to an electrical winding. According to the invention, the detection method is arranged to detect, via a protection device, a failure mode in which the first and second power components are in the on state, said method comprising a step of determining an offset voltage from a measurement voltage of the switching arm and a reference voltage and a detection step arranged to emit an integral signal corresponding to the integral of the offset voltage.

[0032] Such a method makes it possible to detect a failure of one of the power components in an efficient, rapid, reliable, space-saving and inexpensive manner.

[0033] The present invention may be better understood by reading the detailed description which follows, non-limiting examples of implementation of the invention and by examining the attached drawings.

[0034] [Fig.l] schematically and partially represents a rotating electrical machine comprising a voltage converter connected to an electrical network according to an exemplary implementation of the invention.

[0035] [Fig.2] partially represents a mechatronic plan showing a switching arm and a first example of a protection device according to an implementation of the invention.

[0036] [Fig.3] represents, schematically and partially, a top view of the voltage converter of [Fig.l].

[0037] [Fig.4] represents, schematically and partially, a part of a second example of a protection device according to another implementation of the invention.

[0038] [Fig.5] illustrates several curves representing an example of an integral signal and a comparison signal.

[0039] [Fig.6] represents, schematically and partially, a logic diagram of a method for protecting a switching arm of a voltage converter according to an exemplary implementation of the invention.

[0040] Identical, similar or analogous elements retain the same references from one figure to another. It will also be noted that the different figures are not necessarily on the same scale. Furthermore, the exemplary embodiments which are described below are in no way limiting. In particular, it will be possible to imagine variants of the invention comprising only a selection of characteristics described below isolated from the other characteristics described. In particular, all the variants and all the embodiments described can be combined with each other if nothing prevents this combination on the technical level.

[0041] [Fig.l] represents an example of a polyphase rotating electrical machine 10, in particular for a vehicle such as a motor vehicle or a drone, connected to an electrical network comprising in particular a battery 11. The machine is connected to the battery via a positive terminal B+ and a ground terminal GND. This machine 10 transforms mechanical energy into electrical energy and therefore supplies the electrical network via terminal B+ with direct current, in alternator mode, and can operate in motor mode to transform electrical energy into mechanical energy while being supplied by the electrical network via said terminal B+. This rotating electrical machine 10 is, for example, an alternator, an alternator-starter, a reversible machine or an electric motor. The machine can be of the synchronous or asynchronous type.

[0042] In this example, the machine 10 comprises a housing on which a voltage converter 15 is mounted. Alternatively, the voltage converter can be remote from the machine or mounted inside the housing.

[0043] Inside this housing, the machine 10 comprises a rotor 12 integral in rotation with a shaft and a stator 13. The rotor 12 may for example be a claw rotor comprising two pole wheels and an electric coil or be formed from a stack of laminations housing permanent magnets or even a squirrel cage rotor. The stator 13 may comprise a body on which an electric winding is mounted. The winding is formed from one or more phases, also called an electric winding, comprising at least one electric conductor. The winding may be of the corrugated or concentric type and may be formed by one or more electric wires or by a plurality of conductive segments in the form of a bar or a pin. In the example illustrated in [Fig.l], the electric winding comprises three electric phases 14. Alternatively, the electric winding could comprise another number of electric phases such as five or six electric phases.Each phase has one end forming a phase output which is electrically connected to the voltage converter 15. .

[0044] The rotating electrical machine 10 is electrically interfaced via the voltage converter 15 to the electrical network via terminal B+. The voltage converter 15 comprises at least one switching arm 16 for each phase 14. In the example illustrated in [Fig.l], the voltage converter 15 comprises three switching arms 16.

[0045] Each switching arm 16 comprises a ground terminal 17 electrically connected to the electrical ground terminal GND of the electrical network, a power supply terminal 18 electrically connected to a positive terminal B+ of the electrical network, a first and a second power component Q1, Q2, a power supply terminal 19 electrically connected to a positive terminal B+ of the electrical network, a first and a second power component Q1, Q2, a power supply terminal 20 electrically connected to a positive terminal B+ of the electrical network, a second power component Q1, Q2, a power supply terminal 21 electrically connected to a positive terminal B+ of the electrical network, a second power component Q1, Q2, a power supply terminal 22 electrically connected to a positive terminal B+ of the electrical network, a second power component Q1, Q2, a power supply terminal 23 electrically connected to a positive terminal B+ of the electrical network, a second power component Q1, Q2, a power supply terminal 24 electrically connected to a positive terminal B+ of the electrical network, a second power component Q1, Q phase 19 arranged between the first power component Q1 and the second power component Q2 and electrically connected to an electrical phase 14. The first power component Q1 is arranged between the power terminal 18 and the phase terminal 19 and the second power component Q2 is arranged between the ground terminal 17 and said phase terminal 19. Each power component operates as a switch arranged to switch between an off state and an on state. In the off state, the switch is open and electric current does not flow through the component. In the on state, the switch is closed and electric current flows through the component. The on state may correspond to a deliberately on state when the component is driven or an involuntarily on state when a failure of the component causes a short circuit of said component.Each power component Q1, Q2 may comprise a control terminal 20 connected to a control module 21 of the power component and making it possible to control said component between the on state and the off state. In this example, each power component Q1, Q2 is a transistor, in particular of the MOSFET type.

[0046] The voltage converter 15 comprises a protection device 22 for the switching arm 16, shown in [Fig. 2]. The protection device makes it possible to detect a failure mode in which the first and second power components Q1, Q2 of the same switching arm 16 are both in the on state at the same time. [Fig. 2] illustrates an example of a protection device 22 associated with a switching arm 16. Only a portion comprising the power component Q2 of the arm is shown in [Fig. 2].

[0047] The protection device 22 comprises a measurement module 23. The measurement module 23 makes it possible to determine an offset voltage which will be transmitted to the input of a detection module 24 of the protection device 22. The offset voltage is determined by calculating a difference between a measurement voltage of the switching arm 16 and a reference voltage of the voltage converter 15. The difference is for example calculated by taking the difference between said two voltages. For example, the measurement module 23 comprises a resistor RI and an inductor L1 arranged in series making it possible to determine said difference.

[0048] In the failure mode in which both power components Q1, Q2 of the switching arm 16 are in an on state, the voltage across the ground terminal 14 of the switching arm deviates from the voltage across the ground terminal GND of the voltage converter 15.

[0049] In the embodiment shown in [Fig. 2], the measuring voltage of the switching arm is measured at the ground terminal 17 of the switching arm 16. For example, a resistor R2 can be arranged at the ground terminal 17, and in particular between the second power component Q2 and the ground terminal 17, the offset voltage can then be measured across the terminals of resistor R2. Alternatively, the offset voltage can be measured by any other means or taken directly from a point on an electrical trace forming the ground terminal 17 of the switching arm 16.

[0050] Still in the example of [Fig.2], the reference voltage corresponds to the voltage of the ground terminal GND of the voltage converter 15. It is therefore a voltage of the same nature as that of the measurement voltage, here a ground voltage. The reference voltage is preferably taken so as to have a cleaner signal than that of the measurement voltage. For example, the reference voltage can be measured outside a switching zone formed by the switching arm. More precisely, as illustrated in the example of [Fig.3], the voltage converter 15 comprises several power modules 8 each comprising at least one switching arm 16. The voltage converter can also comprise several filtering capacitors 9 which can be associated or not with a power module 8. The filtering capacitors can also be part of the switching zone. As visible in the example of [Fig.3], each switching arm 16 comprises a filtering capacitor 9 connected between the power supply terminal 18 and the ground terminal 17. The filtering capacitor 9 is connected in parallel with the power components Q1, Q2. Still in this example, the voltage converter comprises a capacitor module formed from several filtering capacitors 9 arranged independently of the power modules 8.

[0051] Alternatively, in an embodiment not shown, the measurement voltage of the switching arm can be measured at the supply terminal 18 of the switching arm 16 and the reference voltage can be measured at the positive terminal B+ of the voltage converter 15. The measurement module 23 can then determine an offset voltage corresponding to the difference between said two voltages of the supply terminal and the positive terminal in the same manner as described previously.

[0052] For example, the measurement module 23 can also include a filtering capacitor Cl, visible in [Fig.2], making it possible to smooth the offset voltage.

[0053] The protection device 22 further comprises a detection module 24 receiving as input the offset voltage from the measurement module 23. The detection module 24 makes it possible to shape the offset voltage to emit an integral signal at the output of said module 24. The integral signal therefore corresponds to the integral of the offset voltage to which an offset O or voltage offset may or may not be applied.

[0054] The detection module 24 comprises a capacitor C2 arranged between a ground potential and an output terminal 25 of the detection module, a first resistor R3 arranged between an input terminal 26 of the detection module and said output terminal 25 and a second resistor R4 arranged between a ground potential and the output terminal 25. The capacitor C2 and the resistor R4 are arranged in parallel with each other. The combination of capacitance and resistances allows the slope of curve I, illustrated in [Fig.5], representing the integral of the offset voltage to be defined. The combination of resistances also allows a voltage offset O to be applied to said curve I to prevent the value of the integral from reaching a negative voltage value.

[0055] The detection module 24 may comprise a protection diode DI arranged between the first resistor R3 and the input terminal 26. The diode makes it possible to prevent the electric current from flowing from the detection module to the measurement module 23.

[0056] [Fig.4] illustrates another embodiment of the detection module 24. In this embodiment, the detection module 24 may comprise a diode D2, in particular of the Zener diode type, arranged between the input terminal 26 and the first resistor R3. In particular in this example, the diode D2 is arranged between the diode DI and the first resistor R3. The Zener type diode makes it possible to filter the received offset voltage before it is shaped into an integral signal, which makes it possible to have a more precise integral signal.

[0057] The detection module 24 may also comprise a third resistor R5, visible in [Fig.4], arranged between the capacitor C1 and the first resistor R3 and the second resistor R4. The resistor makes it possible to slow down the slope of the integral to avoid false detection of the failure mode and may be associated with the first mode or the second embodiment of said detection module 24.

[0058] The protection device 22 may comprise a comparison module 27. The comparison module 27 receives as input the integral signal from the detection module 24 and outputs a comparison signal. In this example, the comparison module 27 comprises a comparator for comparing the integral signal with a threshold signal to determine the comparison signal.

[0059] In the example of [Fig.2], the comparison module 27 comprises a comparator 28 in the form of an operational amplifier. The comparator 28 receives the integral signal at one of its inputs and the threshold signal at the other of its inputs. The threshold signal is, for example, a constant threshold voltage. The threshold voltage is, for example, determined from a voltage V to which a voltage divider bridge, in particular formed of two resistors R6, R7, is applied.

[0060] In the example of [Fig.4], the comparison module 27 comprises a comparator 29 in the form of a voltage regulator of type TL431. The threshold signal is then an internal value of the comparator 29.

[0061] When the integral signal is greater than the threshold value then the comparison signal is active and when the integral signal is less than said threshold value, then the comparison signal is inactive. The comparison signal takes the form, for example, of a square wave signal whose voltage is equal to 0V when the signal is inactive and whose voltage is equal to a certain voltage value different from 0V when the signal is active.

[0062] [Fig.5] illustrates a graph comprising several curves and whose ordinate axis is the voltage U and the abscissa axis is the time t. Curve I corresponds to the integral signal, curve S corresponds to the threshold signal and curve E corresponds to the comparison signal. As explained previously, curve E is active when curve I crosses and exceeds curve S.

[0063] The protection device 22 may also comprise a storage module 30 receiving the comparison signal and emitting an error signal in the event of detection of the failure mode, i.e. when the comparison signal is active. In the example of [Fig.2], the storage module 30 is independent of the comparison module 27. In the example of [Fig.4], the storage module 30 and the comparison module 27 form a single module.

[0064] Alternatively, the comparison module and the storage module can be made in a different way and can be made via a voltage converter control module or even be made at the vehicle computer level.

[0065] As described previously, the protection device 22 makes it possible to carry out a protection method 50 of a switching arm 16 making it possible to detect a failure mode in which the first and second power components Q1, Q2 are in the on state. The method 50 comprises a step 51 of determining the offset voltage and a detection step 52 arranged to emit the integral signal. The method 50 may also comprise a comparison step 53 for emitting the comparison signal and a warning step 54 for emitting the error signal.

[0066] The machine 10 preferably comprises a protection device 22 for each of its switching arms 16. The protection devices may be identical or have variants according to the embodiments described previously.

[0067] The present invention finds applications in particular in the field of voltage converters for alternators or reversible machines or electric motors, but it could also be applied to any type of rotating machine. Alternatively, the present invention finds applications in DC-DC voltage converters. The phase terminal is then electrically connected to a winding of a transformer.

[0068] Of course, the preceding description has been given by way of example only and does not limit the scope of the present invention, which would not be exceeded by replacing the various elements with any other equivalents. For example, it has been described above previously embodiments comprising electronic components making it possible to carry out the desired functions. It will not go beyond the scope of the invention to replace these components with software applications making it possible to carry out the same functions.

Claims

Claims

1. Voltage converter intended to be electrically connected to an electrical network, the voltage converter (15) comprising at least one switching arm (16) comprising: - a ground terminal (17) intended to be electrically connected to an electrical ground (GND) of the electrical network, - a power supply terminal (18) intended to be electrically connected to a positive terminal (B+) of the electrical network, - a first and a second power component (Q1, Q2) each operating as a switch arranged to switch between a blocked state and a passing state, the power components being arranged in series with respect to each other between the ground terminal (17) and the power supply terminal (18), - a phase terminal (19) arranged between the first power component (Q1) and the second power component (Q2) and being intended to be electrically connected to an electrical winding (14), the voltage converter (15) being characterized in that it further comprises a protection device (22) for the switching arm (16) configured to detect a failure mode in which the first and second power components (Q1, Q2) are in the on state, the protection device (22) comprising a measurement module (23) arranged to emit an offset voltage from a measurement voltage of the switching arm and a reference voltage and a detection module (24) arranged to emit an integral signal corresponding to the integral of the offset voltage, the measurement voltage being measured at a point of an electrical trace, the detection module (24) receiving as input the offset voltage from the measurement module (23) and making it possible to shape the offset voltage to emit at the output of said module (24) an integral signal therefore corresponding to the integral of the offset voltage to which an offset O or voltage offset may or may not be applied.

2. Voltage converter according to the preceding claim, characterized in that the measuring voltage of the switching arm is measured at at the mass terminal (17) or at the power terminal (18) of the switching arm.

3. Voltage converter according to any one of the preceding claims, characterized in that the detection module (24) comprises a capacitor (Cl) arranged between a ground potential and an output terminal (25) of the detection module, a first resistor (R3) arranged between an input terminal (26) of the detection module and said output terminal (25) and a second resistor (R4) arranged between a ground potential and the output terminal (25) of the detection module.

4. Voltage converter according to the preceding claim, characterized in that the detection module (24) further comprises a Zener diode arranged between the input terminal (26) and the first resistor (R3).

5. Voltage converter according to the preceding claim, characterized in that the detection module (24) further comprises a third resistor (R5) arranged between the capacitor (Cl) and the first resistor (R3) and the second resistor (R4).

6. Voltage converter according to any one of the preceding claims, characterized in that the protection device (22) further comprises a comparison module (27) arranged to emit a comparison signal making it possible to determine whether the integral signal is greater than a threshold value.

7. Voltage converter according to the preceding claim, characterized in that the protection device (22) further comprises a storage module (30) arranged to emit an error signal when the failure mode is detected.

8. A rotating electrical machine comprising a voltage converter (15) according to any one of the preceding claims.

9. Method for protecting a switching arm (16) of a voltage converter (15) according to any one of the preceding claims intended to be electrically connected to an electrical network, the switching arm (16) comprising: - a ground terminal (17) intended to be electrically connected to an electrical ground (GND) of the electrical network, - a power supply terminal (18) intended to be electrically connected to a positive terminal (B+) of the electrical network, - a first and a second power component (Q1, Q2) each operating as a switch arranged to switch between a blocked state and an on state, the power components being arranged in series with each other between the ground terminal (17) and the power supply terminal (18), - a phase terminal (19) arranged between the first power component (Q1) and the second power component (Q2) and being intended to be electrically connected to an electrical winding (14), the detection method (50) being characterized in that it is arranged to detect, via a protection device (22), a failure mode in which the first and second power components are in the on state (Ql, Q2), said method (50) comprising a step of determining (51) an offset voltage from a measurement voltage of the switching arm and a reference voltage and a detection step (52) arranged to emit an integral signal corresponding to the integral of the offset voltage.

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