METHOD FOR DETERMINING A CURRENT FLOWING THROUGH AT LEAST ONE SWITCHING ELEMENT, ELECTRICAL CIRCUIT ARRANGEMENT, AND MOTOR VEHICLE

Abstract

A method determines a current flowing through at least one switching element of an electrical circuit arrangement. When the switching element is turned on the current flows through a switchable portion of the switching element. The switching element is associated with a temperature sensor and a voltage sensor. The temperature sensor measures a temperature of the switching element and the voltage sensor measures a voltage drop across the switchable portion of the switching element. The temperature sensor and the voltage sensor are connected to a computing device. The computing device determines a current value of the current based on the measured temperature and the measured voltage drop.

Claims

1. A method, comprising: turning on a switching element of an electrical circuit arrangement; flowing a current through a switchable portion of the switching element; measuring a temperature of the switching element with a temperature sensor connected to a computing device; measuring a voltage drop across the switchable portion of the switching element with a voltage sensor connected to the computing device; and determining a current value of the current with the computing device based on the temperature measured by the temperature sensor and based on the voltage drop measured by the voltage sensor.

2. The method according to claim 1, comprising: measuring the temperature continuously with the temperature sensor; measuring the voltage drop continuously with the voltage sensor; and continuously determining the current value with the computing device based on the continuously measured temperature and the continuously measured voltage drop.

3. The method according to claim 1, wherein the electrical circuit arrangement includes multiple switching elements each associated with a respective temperature sensor and a respective voltage sensor, wherein the computing device determines for each of the switching elements a respective current value of the current flowing respectively through the switchable portion.

4. The method according to claim 3, wherein the electrical circuit arrangement is a three-phase pulse inverter, wherein the computing device determines the three phase currents from the current values ascertained for at least two of the switching elements.

5. The method according to claim 1, wherein the current value is determined as a function of the magnitude of a control voltage imposed on the switching element in the On condition.

6. The method according to claim 1, wherein the computing device is adapted to operate a driver circuit of the electrical circuit arrangement, in which the switching element is switched by the driver circuit based on the current value.

7. The method according to claim 1, wherein the temperature sensor and the voltage sensor are connected to at least one analog-to-digital converter configured to generate a digital temperature value and a digital voltage value wherein the digital temperature value and the digital voltage value are relayed to the computing device by a galvanically separating connection.

8. The method according to claim 1, wherein the switching element is integrated in a power supply module with at least a portion of the temperature sensor.

9. The method according to claim 1, wherein the temperature sensor includes a temperature-dependent electrical resistance.

10. The method according to claim 1, wherein the switching element is a metal oxide semiconductor field-effect transistor based on silicon carbide.

11. An electrical circuit arrangement, comprising: at least one switching element having a switchable portion; a temperature sensor configured to measure a temperature of the switching element; a voltage sensor configured to measure a voltage drop across the switchable portion; and a computing device connected to the temperature sensor and the voltage sensor and configured to measure a current flowing through the switching element based on the temperature measured by the temperature sensor and based on the voltage drop measured by the voltage sensor.

12. A motor vehicle comprising an electrical circuit arrangement, the electrical arrangement including: at least one switching element having a switchable portion; a temperature sensor configured to measure a temperature of the switching element; a voltage sensor configured to measure a voltage drop across the switchable portion; and a computing device connected to the temperature sensor and the voltage sensor and configured to measure a current flowing through the switching element based on the temperature measured by the temperature sensor and based on the voltage drop measured by the voltage sensor.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0037] Further advantages and details of the present disclosure will emerge from the following described embodiments as well as the drawings.

[0038] FIG. 1 is an illustration of a motor vehicle according to one embodiment.

[0039] FIG. 2 a schematic diagram of a circuit arrangement according to one embodiment.

[0040] FIG. 3 is schematic diagram of an electrical circuit arrangement according to one embodiment.

[0041] FIG. 4 is a schematic diagram of a circuit arrangement according to a method according to one embodiment.

DETAILED DESCRIPTION

[0042] FIG. 1 shows an embodiment of a motor vehicle 1 according to the present disclosure. The motor vehicle 1 includes an electrical circuit arrangement 2, which is designed as a three-phase traction inverter of the motor vehicle 1. The electrical circuit arrangement 2 transforms a direct current taken from a traction energy accumulator 3, such as a high-voltage battery, of the motor vehicle 1 into a three-phase alternating current, for example, for the operation of an electrical traction motor 4 of the motor vehicle 1.

[0043] FIG. 2 shows an embodiment of the electrical circuit arrangement 2. The electrical circuit arrangement 2 is designed as a three-phase pulse inverter and includes six switching elements S.sub.1-S.sub.6. The switching elements S.sub.1 and S.sub.4, S.sub.2 and S.sub.5 and S.sub.3 and S.sub.6 each form a half-bridge, the switching elements S.sub.1-S.sub.3 each representing the high-side transistors and the switching elements S.sub.4-S.sub.6 accordingly the low-side transistors.

[0044] The terminals designated as HV+ and HV− at the direct current side of the electrical circuit arrangement 2 are connected for example to the traction energy accumulator 3 of the motor vehicle 1. Between these terminals is hooked up an intermediate circuit capacitor 6. The bridge points of the respective half-bridges 5 form phase terminals U, V and W for the connection of the electrical traction motor 4. Thanks to the electrical circuit arrangement 2, a direct current taken from the traction energy accumulator 3 can be transformed into a three-phase alternating current with the phase currents I.sub.U, I.sub.V and I.sub.W, in order to operate the electrical traction motor 4. Conversely, an alternating current generated by the traction motor 4 in a generator operation can be transformed into a direct current for the charging of the traction energy accumulator 3.

[0045] The electrical circuit arrangement 2 furthermore includes a computing device 7 as well as a driver circuit 8, the computing device 7 being adapted to operate the driver circuit 8. The driver circuit 8 serves for applying a control voltage or a gate-source voltage U.sub.G1-U.sub.G6 to the switching elements S.sub.1-S.sub.6. The connections between the driver circuit 8 and the control terminals of the switching elements S.sub.1-S.sub.6 are not shown, for reasons of clarity.

[0046] The switching elements S.sub.1-S.sub.6 are designed, e.g., as MOSFETs based on silicon carbide. The switching elements S.sub.1-S.sub.6 each include a switchable portion, across which a current flows when the switching element is turned on. The switchable portions of the switching elements S.sub.1-S.sub.6 are respectively the drain-source sections through which a load current flows when the corresponding switching element has been made conductive by the driver circuit 8, especially to generate the phase currents I.sub.U, I.sub.V and/or I.sub.W in a clocked operation.

[0047] As shown schematically in FIG. 3 for the switching element S.sub.1, the switching element S.sub.1 is associated with a temperature sensor 9 and a voltage sensor 10 of the electrical circuit arrangement 2. As an equivalent diagram for the switching element S.sub.1, there is shown the electrical resistance of the switchable portion R.sub.DS,on, also known as the channel resistance, which results in the activated condition of the switching element S.sub.1. This switchable portion is associated with the temperature sensor 9, by which the temperature of the switchable portion or a junction temperature of the switching element can be measured. The temperature sensor 9 includes a temperature-dependent electrical resistance 10. This may be designed, for example, as a NTC resistance or as a PTC resistance.

[0048] The voltage sensor 10 can be connected to two contacts 11, 12, which are arranged at the drain-source section of the switching element S.sub.1, or it may include these contacts. The temperature sensor 9 is connected across a preamplifier 13 to an analog-digital converter 14, which in the present case is designed as a sigma-delta modulator. Furthermore, a reference voltage source 15 is also shown. The contacts 11, 12 by which the voltage of the switchable portion, i.e., the drain-source voltage of the switching element S.sub.1, can be picked off are likewise connected across a preamplifier 13 to an analog-digital converter 14. The amplifier 13 and the analog-digital converter 14 represent the voltage sensor 10 in this embodiment.

[0049] The preamplifiers 13, the analog-digital converters 14 and the reference voltage sources 15 may each be designed as part of the driver circuit 8 and be arranged, e.g., with the other elements of the driver circuit 8 on a common circuit board. The temperature sensor 9, especially the temperature-dependent resistance 10, is integrated with the switching element S.sub.1 in a power supply module 16. The power supply module 16 may also include, in particular, the switching element S.sub.4 and thus a complete half-bridge 5. In this case, the temperature sensor 9 associated with the switching element S.sub.4, especially the temperature-dependent electrical resistance 10, can also be integrated in the power supply module 16.

[0050] The measurement values of the temperature sensor 9 and the voltage sensor 10, digitalized by the analog-digital converter 14, are relayed by a galvanically separating connection 17 to the computing device 9. The galvanically separating connection 17 includes at least one insulating means 18, as well as multiple transmitters 19 and receivers 20 for relaying the digitalized measurement values of the temperature sensor 9 and the voltage sensor 10. Furthermore, interfaces 21 are provided for connecting the computing device 9 to the galvanically separating connection 17 and thus to the temperature sensor 9 and the voltage sensor 10.

[0051] The components represented in FIG. 3 for the switching element S.sub.1 are present in particular for each of the switching elements S.sub.1-S.sub.6 of the electrical circuit arrangement 2, so that also for the switching elements S.sub.2-S.sub.6 there are present and correspondingly arranged a temperature sensor 9, a voltage sensor 10, and the components 13-15 and 19-21 utilized for the evaluation and transmission of the measurement values to the computing device 9.

[0052] FIG. 4 shows a schematic equivalent diagram of the electrical circuit arrangement 2 to explain an embodiment of a method for determination of a current flowing through at least one of the switching elements S.sub.1-S.sub.6 of the electrical circuit arrangement 2. The method can be carried out by the computing device 7 which, as shown in FIG. 3, is connected respectively to a temperature sensor 9 and a voltage sensor 10 of the switching elements S.sub.1-S.sub.6.

[0053] Schematically represented in the equivalent diagram are the respective resistances R.sub.DS,on,S1-R.sub.DS,on,S6. Each of these represents the temperature-dependent electrical resistance of the switchable drain-source sections of the switching elements S.sub.1-S.sub.6. The temperature sensor 9 respectively measure a temperature of the respectively associated switching element S.sub.1-S.sub.6. With the voltage sensor 10, the voltage drop across the switchable portion of the switching elements S.sub.1-S.sub.6 is measured accordingly. The computing device ascertains a current value of the respective currents I.sub.S1-I.sub.S6. To determine the current Isi, the temperature measured value of the temperature sensor 9 of the switching element S.sub.1 and the voltage measured value of the voltage sensor 10 of the switching element S.sub.1 are used. The other load currents can be determined accordingly by the temperature sensor 9 and voltage sensor 10 which are associated with the other switching elements S.sub.2 to S.sub.5.

[0054] Temperature measured values and voltage measured values are measured continuously by the temperature sensor 9 and the voltage sensor 10, and from these the computing device continuously determines current measurement values. For example, from the temperature measured values the computing device 7 can determine a resistance value of the temperature-dependent channel resistance R.sub.DS,on, in dependence on a value mapping instruction which is embedded for example in the computing device 7. This value mapping instruction may be, for example, a computation instruction or an embedded table. In addition, it is possible for the computing device 7 to also take into account measured values of the respective control voltages U.sub.G1-U.sub.G6, since the control voltage may also have an impact on the magnitude of the resistance R.sub.DS,on especially in the case of a silicon carbide MOSFET.

[0055] Due to measuring all the currents I.sub.S1-I.sub.S6 through the switching elements S.sub.1-S.sub.6, a redundancy can be created, which can advantageously influence the precision of the current measurement and/or the robustness of the electrical circuit arrangement. From the current values I.sub.S1-I.sub.S6 so determined, the phase currents I.sub.U, I.sub.V and I.sub.W can be determined. These correspond to at least one of the determined current values of the currents I.sub.S1-I.sub.S6, depending on the switching condition of the switching elements S.sub.1, so that they can be calculated from the latter.

[0056] Alternatively, it is also possible to not provide a temperature sensor 9 and/or a voltage sensor 10 at all switching elements S.sub.1-S.sub.6 and thus not determine a current value for each of the switching elements. For example, a current value can be determined only for the high-side transistors S.sub.1-S.sub.3. It is also possible to determine a current value for only two of the high-side transistors S.sub.1-S.sub.3. For example, in this case a remaining third current value for one of the phase currents I.sub.U, I.sub.V or I.sub.W can be calculated from the two ascertained current values, for example when there is a star or triangle circuit for the phases U, V, W in the electric machine 4.

[0057] A method according to one embodiment, advantageously makes it possible to do away with additional current sensors for measuring the phase currents I.sub.U, I.sub.V and I.sub.W. In this way, the circuit arrangement 2 can be produced more economically, smaller and more efficient. Furthermore, the robustness of the electrical circuit arrangement 2 is enhanced, since fewer elements or power connections are provided. Furthermore, the overall layout of the electrical circuit arrangement 2 is simplified by the integration of part of the measurement means and/or the galvanically separating connection 17 in the driver circuit 8. This in particular also makes it easier to install the electrical circuit arrangement 2 in the motor vehicle 1.

[0058] The driver circuit 8 for example can be arranged with the inverter, formed from the three half-bridges 5, in a common housing. The computing device 7 can also be arranged inside this housing, or it can be placed in a different position and be connected to the driver device 8 and the temperature sensor 9 and the voltage sensor 10 of the switching elements S.sub.1-S.sub.6.

[0059] The computing device 9 can operate the driver circuit 8 in dependence on the ascertained current values. In particular, the computing device 9 can operate the driver circuit 8 and thus also the switching elements S.sub.1-S.sub.6 in dependence on phase currents I.sub.U, I.sub.V and I.sub.W as determined from the current values I.sub.S1-I.sub.S6, preferably as part of a current regulation of the three-phase motor current for the traction motor 4. For this, the computing device may be connected, for example, to a rotor position sensor (not shown) of the traction motor 4 and/or to a data communication link (not shown), by which rotor position information or a torque setting or the like can be received.

[0060] Due to the robust and compact layout of the electrical circuit arrangement 2, a cooling of the electrical circuit arrangement 2 is also facilitated, for example, by connection to a cooling device (not shown) of the motor vehicle 1. Advantageously, the fault vulnerability of the measurement can be significantly reduced by the integration of the entire measurement chain composed of the temperature sensor 9 and the voltage sensor 10 in the driver circuit 8. Due to the analog-digital converters 14 designed as sigma-delta converters, a digital output signal is advantageously produced, which can minimize the fault vulnerability.

[0061] In one embodiment, a method can also be used in a two-phase inverter or an inverter designed with more than three phases for generating an alternating current. The preceding remarks on the electrical circuit arrangement 2 designed as a three-phase inverter will apply accordingly.

[0062] Patent Application No. 102021113493.5, filed in Germany on May 26, 2021, to which this application claims priority, is hereby incorporated by reference in its entirety.

[0063] Aspects and features of the various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.