Power electronics device, especially for use in a motor vehicle

Abstract

Power electronics device, especially for use in a motor vehicle, comprising: - an electronic device for converting electrical power, wherein an input voltage can be supplied to the electronic device via a first terminal (4) by means of an intermediate circuit energy storage device (8) and the electrical power provided by the input voltage can be converted by means of the electronic device and delivered at a second terminal (5), wherein the electronic device comprises a motor inverter circuit for an electric or hybrid vehicle which converts the input voltage provided at the first terminal (4) via a traction battery (2) into a multi-phase electric motor drive voltage at the second terminal (5); - a power supply (10) for providing an operating voltage for the electronic device, wherein the power supply (10) is supplied with the input voltage via the first connection (4); - wherein the power supply (10) is connected to the intermediate circuit energy storage device (8) in such a way that, upon disconnection of the first connection (4) from the input voltage, the intermediate circuit energy storage device (8) is discharged to 60 volts or less within 120 seconds exclusively via the power supply (10); characterized in that the operating voltage for the motor-inverter circuit is at least partially supplied via an on-board battery during normal operation of the vehicle and the power supply (10) functions as an auxiliary power supply, which provides the entire operating voltage when the on-board battery cannot supply an operating voltage, wherein the motor-inverter circuit is designed in such a way that it short-circuits the phases of the electric motor drive voltage upon detection of an accident.

Description

[0001] The invention relates to a power electronics device, in particular for use in a motor vehicle and especially preferably for use in an electric or hybrid vehicle.

[0002] Power electronics devices are used to convert electrical energy using electronic components and are employed in a wide variety of technical applications. In automotive engineering, power electronics devices include inverters, which convert the voltage of a high-voltage power supply into a multi-phase voltage to drive the vehicle's electric motor. Power electronics devices also exist in the form of chargers and DC-DC converters, which are also used in automotive engineering, for example, to charge the electrical energy storage system of an electric vehicle.

[0003] Typically, a power electronics device incorporates an intermediate circuit energy storage device to convert the electrical energy being processed. This creates the problem that very high voltages can potentially occur in the intermediate circuit energy storage device, which may persist even after the power electronics device is disconnected from the power supply and can be dangerous. Therefore, it is known to incorporate a passive discharge circuit to appropriately discharge the intermediate circuit energy storage device. For example, resistors can be used to convert the energy from the intermediate circuit energy storage device into heat. The use of passive discharge circuits has the disadvantage that additional electrical or electronic components must be integrated into the power electronics device, which in turn increases the device's installation space.Furthermore, the discharge circuit generates waste heat, which reduces the efficiency of the power electronics device. Additionally, adequate cooling must be provided for the discharge circuit, which also increases the installation space of the power electronics device and thus its cost.

[0004] German patent application DE 10 2004 057 693 A1 discloses a device for discharging a DC link capacitor connected to an electric machine in a high-voltage network. The DC link capacitor is discharged via a DC-DC converter connected to an on-board electrical system with an on-board battery. The on-board output voltage of the DC-DC converter is increased when the condition is met that the DC link capacitor is to be discharged.

[0005] German patent application DE 10 2007 022 515 A1 describes a control unit comprising a DC link capacitor and an inverter, the control unit being designed to control an electric machine. To operate the control unit, the inverter is controlled in such a way as to achieve rapid discharge of the DC link capacitor via the windings assigned to the electric machine.

[0006] The object of the invention is to create a power electronics device which enables the discharge of the device's intermediate circuit energy storage in a simple manner.

[0007] This problem is solved by the power electronics device according to claim 1. Further developments of the invention are defined in the dependent claims.

[0008] The power electronics device according to the invention comprises an electronic unit for converting electrical power, wherein an input voltage can be supplied to the electronic unit via a first connection using an intermediate circuit energy storage device, and the electrical power provided by the input voltage can be converted by the electronic unit and delivered at a second connection. The electronic unit of the power electronics device includes a motor-inverter circuit for an electric or hybrid vehicle. This circuit converts the input voltage, which is supplied at the first connection via a traction battery of the electric or hybrid vehicle, into a multiphase electric motor drive voltage at the second connection, i.e., into a voltage intended for driving the electric motor of the electric or hybrid vehicle.

[0009] Furthermore, the power electronics device according to the invention includes a power supply for providing an operating voltage for the electronic device, wherein the power supply is supplied with the input voltage via the first connection. In this way, it is ensured that the power electronics device can also operate without an additional, externally supplied operating voltage. Optionally, the power supply can be designed as an auxiliary power supply, which in normal operation provides no or only a portion of the operating voltage, with the remainder of the operating voltage being derived from an external power supply (e.g., a 12-volt battery in a motor vehicle).

[0010] The power electronics device according to the invention is characterized in that the power supply is connected to the DC link energy storage device in such a way that, when the first connection is disconnected from the input voltage, the DC link energy storage device is discharged exclusively via the power supply. During normal vehicle operation, the operating voltage for the motor-inverter circuit is at least partially supplied by an on-board battery, which serves to supply voltage to secondary consumers in the vehicle. The on-board battery thus differs from a drive or traction battery in an electric or hybrid vehicle. Typically, the on-board battery provides a voltage of 12 volts.Furthermore, the power supply unit of the power electronics device functions as an auxiliary power supply, providing the entire operating voltage when the vehicle's battery cannot supply it, for example, because it is disconnected from the power electronics device due to an accident. If necessary, the auxiliary power supply can also be used during normal operation to supply a portion of the operating voltage. The invention utilizes the fact that the auxiliary power supply can also perform the function of discharging the DC link energy storage device, thus eliminating the need for a separate DC link discharge circuit. In particular, the auxiliary power supply is electrically connected to the DC link energy storage device without the need for an interposed electrical or electronic component and is preferably connected in parallel with the DC link energy storage device.

[0011] The power electronics device according to the invention can have more compact dimensions by eliminating the need for a separate discharge circuit. Furthermore, the device's power loss and heat generation are reduced. This results in an energy-efficient power electronics device that can also be manufactured more cost-effectively than conventional devices.

[0012] A preferred application of the invention is in power electronics devices where a high-voltage input voltage in the range of 100 volts or more, in particular at least 300 volts and preferably at least 400 volts, is provided, since in this case suitable discharge of the DC link energy storage is particularly important due to the high applied voltages. In contrast, the operating voltage for the electronic device (control unit) of the power electronics device according to the invention is preferably in the low-voltage range of 28 volts, particularly preferably at 12 volts.

[0013] In a further preferred embodiment, the power electronics device according to the invention is configured such that, when the first connection is disconnected from the input voltage, the DC link energy storage device is discharged to 60 volts or less via the power supply within a predetermined time period, in particular within 120 seconds. This ensures that the voltages applied to the DC link energy storage device are within a range that is harmless to humans. In a further embodiment of the power electronics device according to the invention, the DC link energy storage device comprises at least one DC link capacitor in a manner known per se.

[0014] The power electronics device according to the invention can be configured for various types of electrical energy conversion. For example, the electronic components of the power electronics device can include a DC-DC converter and / or a charger and / or an inverter. The DC-DC converter can, in particular, be used to convert the voltage of a drive or traction battery of an electric or hybrid vehicle into an on-board voltage (e.g., 12 volts). The charger can, in particular, be used to convert an AC mains voltage supplied externally to an electric or hybrid vehicle via a charging station into the DC voltage of a drive or traction battery.

[0015] In a particularly preferred embodiment, the motor-inverter circuit is designed such that it short-circuits the phases of the electric motor drive voltage upon detection of an accident, thereby ensuring that no dangerous voltages are present on the supply lines to the electric motor after an accident.

[0016] In addition to the power electronics device described above, the invention further relates to a motor vehicle, preferably an electric or hybrid vehicle, which comprises the power electronics device according to the invention or one or more preferred embodiments of the power electronics device according to the invention.

[0017] Exemplary embodiments of the invention are described in detail below with reference to the accompanying figures.

[0018] They show: Fig. 1 the construction of a conventional power electronics device in the form of an inverter for use in an electric or hybrid vehicle; Fig. 2 a modification of the power electronics device with Fig. 1, which additionally includes an active short-circuit circuit; and Fig. 3 the structure of an embodiment of a power electronics device according to the invention.

[0019] Fig. Figure 1 shows a conventional power electronics device configured as an inverter in an electric or hybrid vehicle. The device, designated by reference numeral 1, serves to convert the direct current supplied by the vehicle's high-voltage battery 2 into a three-phase voltage for the vehicle's electric motor 6. Furthermore, during recuperation, the device can supply the power generated by the electric motor 6 to the battery 2 for charging. The high-voltage battery 2, which provides an input voltage in the range of 300 to 600 volts, can be connected to a high-voltage connector 4 of the power electronics device 1 via switches 301 and 302. The motor 6, on the other hand, is connected to the power electronics device 1 via connector 5. The power electronics device includes a converter circuit known per se in the form of three parallel-connected pairs of IGBTs, which are designated with reference numbers 701, 702 and 703 respectively.The IGBTs are controlled by a corresponding controller, which is not included in . Fig. As shown in Figure 1, a three-phase current is carried via lines L1, L2, and L3 to the electric motor 6. Since the Fig. Since the inverter circuit shown is known to the person skilled in the art, its operation will not be explained in further detail.

[0020] To ensure the operation of the inverter circuit, a DC link capacitor 8 is also provided, which is connected in parallel to the pairs of IGBTs and serves to buffer the input voltage supplied by battery 2. DC link capacitors are necessary in almost all power electronics devices to ensure electrical energy conversion even over short time intervals. The power electronics device of the Fig. The intermediate circuit capacitors used are usually very large (capacity from 50 µF to 1.5 mF) so that they can store sufficient energy at the applied high-voltage input voltage to ensure the normal function of the inverter circuit.

[0021] When the power electronics device 1 is disconnected from the high-voltage battery 2 (e.g., during repair or in the event of an accident), the voltage buffered in the intermediate circuit capacitor 8, which is dangerous to humans, is initially present at the high-voltage connector 4. For safety reasons, it is therefore necessary that the intermediate circuit capacitor be discharged appropriately. In particular, it should be ensured that the voltage of the intermediate circuit capacitor drops to a voltage value that is no longer dangerous to humans, e.g., below 60 V, within a predetermined time period (e.g., 120 seconds). To achieve this, the power electronics device is equipped according to... Fig. 1. A passive DC link discharge circuit, known per se, is used, implemented via an electrical component in the form of a resistor 9 connected in parallel to the DC link capacitor 8. However, this discharge circuit has the disadvantage that heat is constantly generated across the resistor 9 during operation of the inverter, causing electrical power losses even when the inverter is not in use. Furthermore, a suitable heat sink must be provided to dissipate the heat, which increases the installation space of the power electronics device.

[0022] Fig. Figure 2 shows a modification of the power electronics device of the Fig. 1, which furthermore includes the function of a so-called active short circuit. Identical or corresponding components are used in the device of the Fig. 2 with the same reference symbols as in Fig. 1. The operating principle of the power electronics device of the Fig. 2 is the same in normal operation as in the device of the Fig. 1. The device also functions as an inverter, with the high voltage of the traction battery 2 of a hybrid or electric vehicle being supplied via connection 4. This voltage is converted by the inverter circuit with the IGBTs 701, 702 and 703 into a three-phase motor voltage at connection 5 for supply to the motor 6. Fig. Figure 2 also shows the drive circuit 11 for the individual gates of the IGBTs 701 to 703. This drive circuit is also used in the device of the Fig. 1 is included, but not explicitly shown there. In normal operation, the drive circuit 11 is controlled by a processor unit 12, which regulates the switching operations of the individual IGBTs such that a multiphase current suitable for driving the motor 6 is carried on lines L1 to L3. The interaction of the drive circuit with the corresponding gates is shown in Fig. 2 indicated by dashed lines L.

[0023] In contrast to the design of the Fig. 1 includes the power electronics device according to Fig. 2. Furthermore, a so-called AKS controller 13 (AKS = Active Short Circuit) is included, which generates an active short circuit in the event of an accident involving the electric or hybrid vehicle. The occurrence of an accident can be detected in a suitable manner, e.g., by triggering airbags. In the case of an active short circuit, the IGBTs are connected in such a way that the three phases of the electric motor are short-circuited, and thus no high voltage is present on lines L1 to L3. This takes into account the possibility that, in the event of an accident, the electric motor 6 may continue to rotate even if the high-voltage battery 2 is disconnected from the power electronics unit and the inverter circuit is switched off. The continued rotation of the motor's wheels then generates voltage, which is fed into the DC link capacitor. Therefore, even after an accident, a high voltage may be present at the DC link, which, for example,Damage to the leads of the power electronics unit 1 to the motor 6 can be dangerous. This danger is eliminated by means of an active short circuit. As mentioned above, the active short circuit is generated via the controller 13, which takes over the control of the gates via the drive circuit 11 whenever a fault is detected according to certain criteria.

[0024] The control components 11, 12, and 13 require an operating voltage, which is normally drawn from the vehicle's 12-volt on-board battery. This leads to the problem that if the power supply to the power electronics unit via the on-board battery is interrupted (as can happen, for example, in an accident), an active short circuit can no longer be generated. Therefore, the power electronics unit... Fig. 2. A separate auxiliary power supply 10 is provided, which supplies the appropriate operating voltage for components 11 to 13 when there is an interruption to the on-board battery. The auxiliary power supply is coupled to the inverter circuit in such a way that it draws current from the high voltage and generates a suitable operating voltage from it, with which the AKS controller 13 can then switch on the lower of the IGBTs 701 to 703 in order to short-circuit the three phases of the electric motor 6. In the circuit of the Fig. 2 is analogous to Fig. 1. A discharge circuit in the form of a resistor 9 is provided, which ensures that the intermediate circuit capacitor 8 is discharged when the high-voltage battery 2 is disconnected from the power electronics device 1. This also results in the problems described above of power loss due to resistance heat and a large installation space.

[0025] To solve these problems, the following will be done in Fig. Figure 3 shows a power electronics device, which represents an embodiment of the invention. The construction of this device largely corresponds to the device of the Fig. 2, whereby the same reference symbols are again used to designate the same or corresponding components. The device of the Fig. 3 is analogous to Fig. 2 a power electronics device in the form of an inverter, which can additionally generate an active short circuit in the event of an accident and also includes an auxiliary power supply 10. The essential difference of the power electronics device of the Fig. 3 compared to the Fig. 2 consists in the fact that the function of discharging the intermediate circuit capacitor 8 is no longer effected via a separate discharge circuit in the form of a resistor 9, but rather the auxiliary power supply 10 is used for this purpose, which can draw current from the intermediate circuit capacitor and consequently discharge it. In the embodiment of the Fig. 3. Thus, the synergy between a converter circuit with an intermediate circuit capacitor and an active short-circuit circuit with an auxiliary power supply is utilized in such a way that the auxiliary power supply now takes over the functionality of discharging the intermediate circuit capacitor.

[0026] The inventors were able to demonstrate that a conventional auxiliary power supply can indeed fulfill the requirements for a discharge circuit for an intermediate circuit capacitor, thus eliminating the need for an additional passive discharge circuit altogether. This saves space within the device. Furthermore, the cost of the power electronics device is reduced, as fewer components are required, resulting in a smaller circuit board and housing. Additionally, the energy density of the power electronics device is increased because there are fewer power losses, and smaller heat sinks can be used since no heat is generated via the resistance of a passive discharge circuit. This, in turn, improves the efficiency of the powertrain in electric and hybrid vehicles.

Claims

[1] Power electronic device, especially for use in a motor vehicle, comprising: - an electronic device for converting electrical power, wherein an input voltage can be supplied to the electronic device via a first terminal (4) by means of an intermediate circuit energy storage device (8) and the electrical power provided by the input voltage can be converted by means of the electronic device and delivered at a second terminal (5), wherein the electronic device comprises a motor inverter circuit for an electric or hybrid vehicle which converts the input voltage provided at the first terminal (4) via a traction battery (2) into a multi-phase electric motor drive voltage at the second terminal (5); - a power supply (10) for providing an operating voltage for the electronic device, wherein the power supply (10) is supplied with the input voltage via the first connection (4); - wherein the power supply (10) is connected to the intermediate circuit energy storage device (8) in such a way that when the first connection (4) is disconnected from the input voltage, the intermediate circuit energy storage device (8) is discharged to 60 volts or less within 120 seconds exclusively via the power supply (10); characterized by, that the operating voltage for the motor inverter circuit is at least partially provided via an on-board battery during normal operation of the vehicle and the power supply (10) acts as an auxiliary power supply which provides the entire operating voltage when the on-board battery cannot supply an operating voltage, wherein the motor inverter circuit is designed such that it short-circuits the phases of the electric motor drive voltage upon detection of an accident. [2] Power electronic device according to claim 1, characterized by , that the power supply (10) is connected to the intermediate circuit energy storage (8) without the interposition of an electrical or electronic component and in particular is connected in parallel with the intermediate circuit energy storage (8). [3] Power electronic device according to claim 1 or 2, characterized bythat the input voltage is 100 volts or more, in particular at least 300 volts and preferably at least 400 volts, whereas the operating voltage for the electronic device is preferably 28 volts or less, particularly preferably 12 volts. [4] Power electronic device according to any one of the preceding claims, characterized by , that the intermediate circuit energy storage (10) includes at least one intermediate circuit capacitor. [5] Power electronic device according to any one of the preceding claims, characterized by that the electronic device includes a DC-DC converter and / or a charger and / or an inverter. [6] Motor vehicle, in particular electric or hybrid vehicle, comprising a power electronics device according to any of the preceding claims.

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