Power module for operating an electric vehicle drive

Abstract

A power module (10) for operating an electric vehicle drive, comprising a plurality of power switches (12, 14, 16) each having a power semiconductor; control electronics (18) for controlling the plurality of power switches (12, 14, 16) in order to generate an output current based on an input current; wherein the control electronics (18) further comprises a temperature unit (24) designed to obtain an operating voltage and an operating current of the power semiconductor and to determine a temperature of the power semiconductor based on the operating voltage and the operating current.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electric mobility, in particular to a power module for operating an electric drive of a vehicle. BACKGROUND

[0002] Power modules, in particular integrated power modules, are increasingly used in motor vehicles. Such power modules are used, for example, in DC / AC inverters, which are used to supply multiphase alternating current to electric machines, for example electric motors. Here, a direct current generated by means of a DC energy source, for example a battery, is converted into a multiphase alternating current. Power modules are based on power semiconductors, in particular transistors, for example IGBTs, MOSFETs and HEMTs. Other application fields are DC / DC converters and AC / DC converters and transformers.

[0003] The power switches used for bridge circuits are usually composed of power semiconductors. One common example is the so-called half-bridge, which comprises a high-side component and a low-side component. The high-side component and the low-side component each comprise one or more power switches, i.e. high-side power switches or low-side power switches. By switching the high-side power switches and the low-side power switches selectively, the direction of the current (output current) generated at the output of the power module can be changed between a positive current direction and a negative current direction in very short cycles. This enables so-called pulse width modulation in order to generate an alternating current on the basis of a direct current fed in at the input side of the power module in the case of a DC / AC inverter.

[0004] It is advantageous in all these applications for the switching times of the power switches used to be sufficiently short. Due to the progress in the field of power semiconductors, short switching times can be achieved using so-called wide bandgap semiconductors (semiconductors with a large bandgap), for example SiC and GaN.

[0005] All power semiconductors have a maximum temperature which must not be exceeded during operation in order not to impair the power semiconductor. Therefore, when designing a power electronic drive, care is taken to ensure that this maximum temperature is adhered to in each operating state. For this purpose, temperature sensors are used to detect the operating temperature of the power switches. Negative temperature coefficient (NTC) sensors and positive temperature coefficient (PTC) sensors are known from the prior art. NTC sensors and PTC sensors are resistors whose resistance value changes depending on the temperature, which has a negative or positive temperature coefficient. Therefore, by measuring the resistance value, the prevailing temperature in the power semiconductor can be inferred.

[0006] However, temperature measurement in power modules, as known from existing technologies, suffers from inaccuracies. This inaccuracy stems from the fact that temperature sensors are typically isolated from the power semiconductors. The measured temperatures often differ significantly from the actual dominant operating temperatures within the power semiconductors, thus rendering them unreliable indicators for evaluating their performance. While computational models can be considered to correct for these temperature deviations, such models can only achieve reliable temperature detection to a limited extent. For example, dynamic temperature jumps cannot be detected using such models. Summary of the Invention

[0007] Therefore, the basic objective of this invention is to realize a power module in which the operating temperature of the power semiconductor is detected with higher accuracy.

[0008] This objective is achieved by a power module and method having the features of the present invention.

[0009] The power modules within the scope of this invention are used to operate electric drives in vehicles, particularly electric and / or hybrid vehicles. The power modules are preferably used in DC / AC inverters. In particular, the power modules are used to power electric machinery (e.g., electric motors and / or generators). DC / AC inverters are used to generate multiphase alternating current from direct current generated by means of a DC voltage from an energy source (e.g., a battery).

[0010] The power module has multiple power switches. These semiconductor-based power switches are used to generate an output current based on the input current fed in, by controlling each power switch. Control of the power switches is achieved by means of control electronics having one or more printed circuit boards on which multiple electronic components are mounted. The control electronics preferably includes a controller component that generates a control signal based on the operating state of the power module and a driver component that controls the power switches based on the control signal. Control can be based on so-called pulse width modulation. In the case of an inverter, the input current is direct current (DC), while the output current is alternating current (AC).

[0011] Multiple power switches preferably form a bridge circuit arrangement, which may include one or more bridge circuits (e.g., half-bridges). Each bridge circuit or half-bridge includes one or more high-side switches (HS switches) connected in parallel with each other and one or more low-side switches (LS switches) connected in parallel with each other. The HS switches / multiple HS switches are connected in series with the LS switches / multiple LS switches. In the case of an inverter, each half-bridge is assigned to one phase of the multiphase alternating current (output current). The HS switches and LS switches each include one or more power semiconductor components, such as IGBTs, MOSFETs, or HEMTs. The semiconductor material on which the respective power semiconductor components are based preferably includes so-called wide-bandgap semiconductors (semiconductors with large band gaps), such as silicon carbide (SiC) or gallium nitride (GaN), and alternatively or additionally may include silicon.

[0012] To cool the power switch and other electronic components in the power module, a cooling body can be provided, with the power switch thermally coupled to the cooling body.

[0013] According to the present invention, the control electronics include a temperature unit designed to obtain the operating voltage and operating current of the power semiconductor, and to determine the temperature of the power semiconductor based on the operating voltage and operating current. The operating current of the power semiconductor can be obtained, for example, by one or more phase current sensors arranged in or interacting with the power module. The operating voltage of the power semiconductor can be directly intercepted at the power semiconductor and thus measured. Alternatively, the operating voltage of the power semiconductor can be approximately obtained, for example, by intercepting a voltage proportional to the voltage drop applied to the power semiconductor. Alternatively or additionally, the operating voltage and / or operating current can be values ​​calculated respectively by means of a computational model or simulation.

[0014] Preferably, the diode is connected upstream of the power semiconductor that acts as a transistor. More preferably, the diode is connected on the side of the transistor's drain electrode away from the transistor's source electrode. In this case, the temperature unit is preferably designed to obtain the diode voltage applied to the diode as the operating voltage of the power semiconductor. It should be understood within the scope of this invention that the diode voltage is a specific form of the operating voltage of the power semiconductor.

[0015] Temperature can be determined in different ways based on the obtained operating voltage and current of the power semiconductor. According to one embodiment, the temperature unit is designed to access a calibration database obtained by means of pre-characterization of the power semiconductor. Preferably, the calibration database is a table containing the values ​​of the operating voltage and current of the power semiconductor recorded at multiple temperatures, along with the corresponding temperature value of the power semiconductor.

[0016] According to another embodiment, the temperature unit is designed to access one or more calibration characteristic curves obtained by plotting the operating voltage based on the operating current at multiple temperatures of the power semiconductor, and / or by plotting the operating current based on the operating voltage at multiple temperatures of the power semiconductor. In this case, one or more calibration characteristic curves contain one or more IV characteristic curves. The obtained pairs of operating voltage and operating current values ​​can be compared with one or more IV characteristic curves to identify the IV characteristic curve containing that pair of values.

[0017] According to another embodiment, the temperature unit is designed to determine the temperature of the power semiconductor using a mathematical function based on voltage-current-value pairs, which describes the behavior of the power semiconductor's temperature in relation to its operating voltage and operating current.

[0018] Because no additional temperature sensor is required to determine the temperature of the power semiconductor, the power module can be manufactured at a lower cost in a particularly cost-effective and compact manner. Furthermore, the present invention completely overcomes the disadvantage of measurement inaccuracy caused by the distance between the temperature sensor and the power semiconductor. The temperature of the power semiconductor determined according to the present invention is particularly accurate because the temperature determination is based on the continuous reading of the operating voltage and current of the power semiconductor during operation. Therefore, the temperature of the power semiconductor can be continuously measured during operation.

[0019] Advantageous design schemes and improvements are provided in the preferred embodiments. Attached Figure Description

[0020] Embodiments will now be described exemplarily and with reference to the accompanying drawings. In the drawings:

[0021] Figure 1 A schematic diagram of a power module according to one embodiment is shown;

[0022] Figure 2 It shows Figure 1 A schematic diagram of the power module circuit; and

[0023] Figure 3 A schematic diagram of a method according to one embodiment is shown.

[0024] In the figures, the same reference numerals refer to the same or similarly functional reference parts. Detailed Implementation

[0025] Figure 1A schematic diagram of a power module 10 according to one embodiment is shown. The power module 10 includes a plurality of power switches 12, 14, 16, each having a power semiconductor. The power semiconductor may be silicon or a so-called wide-bandgap semiconductor (a semiconductor with a large bandgap), such as silicon carbide (SiC) or gallium nitride (GaN). The power module 10 includes control electronics 18 for controlling the power switches 12, 14, 16. The control electronics 18 has a controller component 20 and a driver component 22. The controller component 20 is used to acquire the operating state of the power module and / or the electric vehicle drive, and generate control signals based thereon. The driver component 22 is used to control the power switches based on the control signals, for example, determining the gate voltage, drain voltage, source voltage, drain-source current, and / or source-drain current of the power switch to be controlled.

[0026] Power module 10 in Figure 1 The diagram is simplified. Typically, the power module 10 preferably includes a current input terminal that receives an input current based on an energy source (e.g., a power battery) fed into the input, and a current output terminal that outputs an output current based on the input current generated by power switches 12, 14, 16 under the control of the controlled electronics 18. When the power module 10 is used as an inverter, the AC multiphase output current is preferably generated based on the DC input current by means of pulse width modulation of the power switches 12, 14, 16.

[0027] In addition, power module 10 may have intermediate circuit capacitors for smoothing the input-side voltage and a cooling body for dissipating heat generated during the operation of power switches 12, 14, 16. Power switches 12, 14, 16 may be connected to the cooling body via an insulating layer, such as a direct copper cladding (DBC) layer having two copper layers and an insulating layer disposed therebetween.

[0028] A temperature unit 24 is also arranged in the control electronics 18, particularly in the controller component 20. The temperature unit 24 is used to obtain the operating voltage and operating current of the power semiconductors of one or more power switches 12, 14, 16. Based on the operating voltage and operating current, the temperature unit 24 can determine the temperature of the power semiconductors.

[0029] Figure 2 It shows Figure 1A schematic diagram of the circuit of power module 10 is shown. Only one power switch 12, 14, 16 is shown here in a simplified form; this power switch is designed as a transistor (e.g., IGBT, MOSFET, HEMT). The transistor includes a drain electrode 13, a source electrode 15, and a gate electrode 17. These three electrodes are connected to terminals 38, 40, and 42 of driver component 22 via signal lines, respectively. Driver component 22 is connected to controller component 20, and driver component 22 and controller component together constitute control electronics 18.

[0030] A voltage measurement unit 26 is provided in the power module 10 to determine the operating voltage of the power semiconductor. The operating voltage of the power semiconductor can be the drain-source voltage U. ds The drain-source voltage can be directly captured as the voltage drop applied to the power semiconductor. However, in Figure 2 In the embodiment shown, the diode voltage U is measured by means of the voltage measuring unit 26. d As the operating voltage, the potential intercepted is located at point 28 on the cathode of diode 32, away from the anode of diode 32, and this point is connected upstream of power switches 12, 14, and 16. Specifically, diode 32 is positioned on the side of drain electrode 13 away from source electrode 15. Diode voltage U d With drain-source voltage U ds The voltage is proportional to the voltage applied to the power semiconductor. Diode 32 is preferably a decoupling diode used to decouple high voltages applied to the power semiconductor. When the transistor operates in its conducting phase, a high voltage exists at the power semiconductor. To prevent the high voltage from affecting the driver component 22 or the control electronics 18, the high voltage is decoupled using diode 32.

[0031] Decoupling diode 32 can be as follows Figure 2 The short-circuit detection device 30 is arranged as exemplarily shown, and additionally includes an RC element consisting of a resistor 34 and a capacitor 36. Alternatively, the decoupling diode 32 can be integrated into the active clamping unit, preferably as a Zener diode.

[0032] Drain-source voltage U ds Depends on the operating current I of the power semiconductor (especially the drain-source current I). ds ) and operating temperature T jBased on the obtained operating voltage and current of the power semiconductor, the operating temperature of the power semiconductor can be determined in different ways. According to one embodiment, the temperature unit 24 is designed to access a calibration database obtained by means of pre-characterization of the power semiconductor. Preferably, the calibration database is a table containing the values ​​of the operating voltage and current of the power semiconductor recorded at multiple temperatures, along with the corresponding temperature value of the power semiconductor.

[0033] According to another embodiment, temperature unit 24 is designed to access one or more calibration characteristic curves obtained by plotting operating voltage based on operating current at multiple temperatures of the power semiconductor, and / or by plotting operating current based on operating voltage at multiple temperatures of the power semiconductor. In this case, one or more calibration characteristic curves contain one or more IV characteristic curves. The obtained pairs of operating voltage and operating current values ​​can be compared with one or more IV characteristic curves to identify the IV characteristic curve containing that pair of values.

[0034] According to another embodiment, the temperature unit 24 is designed to determine the temperature of the power semiconductor using a mathematical function based on voltage-current-value pairs, which describes the behavior of the power semiconductor's temperature in relation to its operating voltage and operating current.

[0035] Figure 3 A schematic diagram of a method 100 for determining the temperature in a power module 10 is shown. In a first step 101 of method 100, the operating voltage and operating current of the power semiconductor are obtained by the temperature unit 24 of the control electronics 18. In a second step 102 of method 100, the temperature of the power semiconductor is determined based on the operating voltage and operating current.

[0036] List of reference signs

[0037] 10 Power Modules

[0038] 12, 14, 16 Power Switches

[0039] 13 Drain electrode

[0040] 15 Source Electrode

[0041] 17 Gate electrode

[0042] 18 Control electronic devices

[0043] 20 Controller Components

[0044] 22 Drive components

[0045] 24 Temperature Units

[0046] 26 Voltage Measurement Unit

[0047] 28 points

[0048] 30 Short-circuit detection device

[0049] 32 Diode

[0050] 34 resistors

[0051] 36 capacitors

[0052] 38, 40, 32 terminals

[0053] 100 methods

[0054] Steps 101-102

Claims

1. A power module (10) for operating an electric vehicle drive, comprising: - A plurality of power switches (12, 14, 16), each of the plurality of power switches having a power semiconductor; - Control electronics (18) for controlling the plurality of power switches (12, 14, 16) to generate an output current based on the input current; The control electronics (18) further includes a temperature unit (24) designed to obtain the operating voltage and operating current of the power semiconductor, and to determine the temperature of the power semiconductor based on the operating voltage and operating current. The diode is connected to the drain electrode (13) of the power semiconductor on the side opposite to the source electrode (15) of the power semiconductor, and the temperature unit (24) is designed to obtain the diode voltage (U) applied to the diode (32). d ) is the operating voltage of the power semiconductor, where represents the diode voltage (U) d The potential intercepted by the diode (32) is located at point (28) on the cathode of the diode (32) away from the anode of the diode (32).

2. The power module (10) according to claim 1, wherein the power semiconductor acts as a transistor, and wherein the operating voltage includes the drain-source voltage (Ud) of the power semiconductor. ds ).

3. The power module of claim 1, wherein the diode (32) is designed as a decoupling diode for decoupling a high voltage applied to the power semiconductor.

4. The power module (10) according to any one of claims 1 to 3, wherein the diode (32) is arranged in the short-circuit detection unit (30) and / or active clamping unit of the power module (10).

5. The power module (10) according to any one of claims 2 to 3, wherein the temperature unit (24) is designed to determine the temperature of the power semiconductor by means of a calibration database.

6. The power module according to any one of claims 1 to 3, wherein the power semiconductor acts as a transistor, and wherein the operating current includes the positive drain-source current (I0) of the power semiconductor. ds ).

7. The power module according to any one of claims 1 to 3, wherein the control electronics (18) has a controller component (20) for generating control signals based on the operating state of the power module (10) and / or the electric vehicle drive, and a driver component (22) for controlling the power switches (12, 14, 16) based on the control signals, wherein the temperature unit (24) is arranged in the controller component (20) of the control electronics (18).

8. A method (100) for determining a temperature in a power module, the power module comprising a plurality of power switches (12, 14, 16) each having a power semiconductor, and control electronics (18) for controlling the plurality of power switches (12, 14, 16) to generate an output current based on an input current, the method comprising: - First step (101), wherein the operating voltage and operating current of the power semiconductor are obtained by the temperature unit (24) of the control electronics (18), wherein the diode is connected to the side of the drain electrode (13) of the power semiconductor away from the source electrode (15) of the power semiconductor, wherein the diode voltage (U) applied to the diode (32) is obtained by the temperature unit (24). d ) is the operating voltage of the power semiconductor, where represents the diode voltage (U) d The potential intercepted by the diode (32) is located at point (28) on the cathode of the diode (32) away from the anode of the diode (32); - Second step (102), wherein the temperature of the power semiconductor is determined based on the operating voltage and the operating current.

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