Voltage converter assembly, actuation circuit for an electric drive system, electric drive system, and method for operating an voltage converter assembly

Abstract

The invention relates to a voltage converter assembly having one or more half-bridges. According to the invention, at least one of the half-bridges is designed such that it can also be operated as a synchronous converter. In this way, the half-bridge operated as a synchronous converter can be used to provide an auxiliary DC voltage as required.

Description

[0001] Description

[0002] title

[0003] Voltage converter arrangement, control circuit for an electric drive system, electric drive system and method for operating a voltage converter arrangement

[0004] Technical area

[0005] The present invention relates to a voltage converter arrangement and a method for operating a voltage converter arrangement. The present invention further relates to a control circuit for an electric drive system having such a voltage converter arrangement and to an electric drive system.

[0006] background

[0007] Vehicles that are fully or at least partially electrically powered have an electric drive system. The energy source of such an electric drive system is an electrical energy storage device, such as a traction battery. A voltage converter controls an electric machine using the electrical energy provided by the electrical energy storage device. A so-called intermediate circuit capacitor is usually provided to stabilize the input voltage of the voltage converter.

[0008] When the vehicle is shut down, and especially in a dangerous situation such as an accident, this intermediate circuit capacitor must be discharged as quickly as possible. In addition to passive concepts, active discharge of the intermediate circuit capacitor can also be provided for this purpose. For example, the publication DE 10 2012 210 603 A1 describes a safety concept for batteries that also includes a discharge circuit.

[0009] In order to ensure reliable functionality of the active discharge, the energy supply for such an active discharge must also be guaranteed.

[0010] Disclosure of the invention

[0011] The present invention provides a voltage converter arrangement, a control circuit for an electric drive system, an electric drive system, and a method for operating a voltage converter arrangement having the features of the independent patent claims. Further advantageous embodiments are the subject of the dependent patent claims.

[0012] Accordingly, it is provided:

[0013] A voltage converter arrangement with an input terminal, an output terminal, and at least one half-bridge. The input terminal is designed to be connected to a DC voltage source. Each half-bridge of the at least one half-bridge comprises a first semiconductor switching element and a second semiconductor switching element. The first semiconductor switching element and the second semiconductor switching element are arranged in series. The first semiconductor switching element is arranged between a positive connection point of the input terminal and a node of the respective half-bridge. The second semiconductor switching element is arranged between the node and a negative connection point of the input terminal. Each node of a half-bridge is electrically coupled to a corresponding connection point of the output terminal. Furthermore, one half-bridge of the voltage converter arrangement is additionally designed as a synchronous converter.

[0014] Furthermore, a control circuit for an electric drive system with a voltage converter arrangement according to the invention is provided, wherein the half-bridge configured as a synchronous converter is designed to provide electrical energy for driving driver circuits of the half-bridges in the synchronous converter circuit. Furthermore, the half-bridge configured as a synchronous converter can also provide electrical energy for logic circuits, in particular logic circuits in the voltage converter arrangement, and optionally for other components, such as a discharge circuit for actively discharging an intermediate circuit capacitor.

[0015] Furthermore, it is planned:

[0016] An electric drive system comprising an electric machine and a voltage converter arrangement according to the invention. Each connection point of the output terminal of the voltage converter arrangement is electrically connected to a corresponding terminal of the electric machine.

[0017] Finally, it is planned:

[0018] A method for operating a voltage converter arrangement, in particular a voltage converter arrangement according to the invention. The method comprises a step for operating the half-bridge designed as a synchronous converter as a voltage converter for converting a direct voltage provided at the input terminal into a further voltage. The further voltage is provided at a connection point of the output terminal of the voltage converter arrangement. The method further comprises a step for alternatively operating the half-bridge designed as a synchronous converter as a synchronous converter. The direct voltage provided at the input terminal is converted into an auxiliary voltage. The auxiliary voltage is provided at an output point of the synchronous converter during operation as a synchronous converter.

[0019] If the voltage converter arrangement comprises more than one half-bridge, the method further comprises a step of opening all semiconductor switching elements in the further half-bridges not designed as synchronous converters when the half-bridge designed as a synchronous converter is operated as a synchronous converter.

[0020] Advantages of the invention

[0021] The present invention is based on the realization that, to meet safety requirements in an electric drive system, some components should or must be designed redundantly. Among other things, it may therefore be necessary to implement the power supply for actively discharging a DC link capacitor via at least two redundant paths. However, implementing an additional voltage converter, which provides the required power supply in the event of a low-voltage power supply failure by converting voltage from a high-voltage network or similar, represents a very complex and cost-intensive option.

[0022] It is therefore an idea of ​​the present invention to provide a redundant power supply for at least part of a voltage converter that is simple and cost-effective to implement. In particular, it is an idea of ​​the present invention to make use of existing components or assemblies for this purpose wherever possible. Based on this consideration, the invention provides for expanding a half-bridge of a voltage converter such that it can also be used as a synchronous converter. In this way, such a synchronous converter can also provide electrical energy that is sufficient at least for emergency operation, such as the active discharge of an intermediate circuit capacitor.

[0023] A synchronous converter comprises two switching elements arranged in series, with an inductance, in particular a storage choke, being arranged at the node between the two switching elements. The two switching elements are operated in such a way that they are closed alternately. Preferably, a dead time is provided between the opening of one switching element and the subsequent closing of the other switching element. In this way, short-circuit conditions can be avoided. However, since the basic structure of a synchronous converter is considered to be known, a more detailed explanation of the functional principle and the switching mode of the individual switching elements is omitted here. The configuration of this half-bridge as a synchronous converter comprises a further switching element which can open or close an electrical connection between the half-bridge designed as a synchronous wall and an output point.In this way, the output point can be electrically separated from the half-bridge as long as this half-bridge is not operated as a synchronous wall.

[0024] For the inventive implementation of a synchronous converter, the existing semiconductor switching elements of a half-bridge in the voltage converter arrangement are thus utilized. These can be suitably controlled for operation of the half-bridge as a synchronous converter. In this way, a desired DC voltage can be provided at an output point of the synchronous converter. This DC voltage at the output point of the synchronous converter can be used, for example, to maintain at least emergency operation in the event of a main power supply failure. In this emergency operation, for example, an active discharge of an intermediate circuit capacitor can be performed. Furthermore, any other operations, in particular safety-relevant operations, are of course also possible.

[0025] Operating a half-bridge as a synchronous converter thus provides a redundant power supply, ensuring the necessary safety requirements. By using the existing half-bridge in the voltage converter arrangement, existing circuit structures can be utilized. This reduces the required hardware complexity and the associated costs, as well as the space requirements.

[0026] According to one embodiment, the half-bridge designed as a synchronous converter comprises an inductance. This inductance is, as already explained above, arranged at the node between the first semiconductor switching element and the second semiconductor switching element of the half-bridge designed as a synchronous converter. This inductance thus serves as a storage choke in the synchronous converter. Furthermore, the synchronous converter can comprise a further switching element. This further switching element can be arranged between the inductance and the output point of the synchronous converter. By opening this switching element, the output point is electrically separated from the inductance and thus from the half-bridge. If the half-bridge is to be operated as a synchronous converter, the switching element is closed, whereby the output point is electrically connected to the inductance. In particular, a semiconductor switching element such as a MOSFET can be used as the switching element.

[0027] According to one embodiment, the voltage converter arrangement comprises a control device. The control device is designed to control the semiconductor switching elements of the voltage converter arrangement for voltage conversion between the input terminal and the output terminal in a first operating mode. Furthermore, the control device is designed to control the semiconductor switching elements of the half-bridge configured as a synchronous converter for voltage conversion between the input terminal and the output point of the synchronous converter in a second operating mode. The second operating mode can be implemented in particular if the primary voltage supply for the components controlling the voltage converter arrangement fails.

[0028] According to one embodiment, the voltage converter arrangement comprises at least one further half-bridge in addition to the half-bridge configured as a synchronous converter. The control device can be configured to open the switching elements of the at least one further half-bridge when the half-bridge configured as a synchronous converter is operated as a synchronous converter. In this way, the further half-bridges are deactivated, so that no energy is transferred from the input terminal to the output terminal.

[0029] According to one embodiment, the half-bridge designed as a synchronous converter comprises an overvoltage protection element. The overvoltage protection element can be, for example, a Zener diode. The overvoltage protection element is arranged between the output point of the synchronous converter and a reference potential. This ensures that excessive voltage is not applied at the output point of the synchronous converter, which could potentially damage the components supplied with power by the synchronous converter.

[0030] According to one embodiment, the control circuit for an electric drive system comprises a discharge circuit. This discharge circuit can be designed to actively discharge an intermediate circuit capacitor. Such an intermediate circuit capacitor can, for example, be provided at the input terminal of the voltage converter arrangement. In this way, the intermediate circuit capacitor can stabilize the input voltage of the voltage converter arrangement during operation. The half-bridge designed as a synchronous converter can be designed to provide electrical energy to the discharge circuit. The synchronous converter thus provides, in addition to a further conventional energy supply, for example from a low-voltage network of a

[0031] Electric vehicle, an additional redundant power supply. This allows a safe discharge of the intermediate circuit capacitor even if the primary power supply of the discharge circuit is interrupted.

[0032] The above embodiments and further developments can be combined with one another as desired, where appropriate. Further embodiments, further developments, and implementations of the invention also include combinations of features of the invention not explicitly mentioned above or described below with respect to the exemplary embodiments. In particular, those skilled in the art will also add individual aspects as improvements or additions to the respective basic forms of the invention.

[0033] Short description of the drawings

[0034] Further features and advantages of the invention are explained below with reference to the figures. These show:

[0035] Fig. 1: a schematic representation of a basic circuit diagram of an electric drive system with a voltage converter arrangement according to an embodiment; Fig. 2: a schematic representation of a basic circuit diagram of a half-bridge designed as a synchronous converter in a voltage converter arrangement according to an embodiment; and

[0036] Fig. 3: a flowchart underlying a method for operating a voltage converter arrangement according to an embodiment.

[0037] Description of embodiments

[0038] Figure 1 shows a schematic representation of a basic circuit diagram of an electric drive system with a voltage converter assembly 1 according to one embodiment. Although the voltage converter assembly 1 is described below in connection with an electric drive system, in particular an electric drive system for a fully or partially electrically powered vehicle, the voltage converter assembly according to the invention is not limited to this. Rather, the voltage converter assembly 1 can also be used for any other suitable applications.

[0039] The voltage converter arrangement 1 comprises an input terminal 11 and an output terminal 12. The input terminal 11 can be electrically coupled to a DC voltage source 2, for example, the traction battery of an electric vehicle. A disconnect switch 4 can be provided between the DC voltage source 2 and the input terminal 11 of the voltage converter arrangement 1, which disconnect switch 4 electrically connects or disconnects the DC voltage source 2 to the input terminal 11. Furthermore, an intermediate circuit capacitor 5 can be provided, which, for example, stabilizes the DC voltage at the input terminal 11 of the voltage converter arrangement 1. Furthermore, a discharge circuit 6 can be provided in parallel with the intermediate circuit capacitor 5. This discharge circuit 6 can actively discharge the intermediate circuit capacitor 5 as needed. A primary power supply (not shown here) can be provided for the operation and control of the discharge circuit 6.

[0040] For example, in an electric vehicle, this primary power supply can be provided by a low-voltage network. Furthermore, as explained in more detail below, an additional, redundant power supply can be provided for the discharge circuit 6.

[0041] An electrical load 3, for example, an electrical machine, can be provided at the output terminal 12 of the voltage converter assembly 1. To operate this electrical load 3, the voltage converter assembly 1 can convert a DC voltage provided on the input side into another voltage suitable for operating the electrical load 3. For example, the voltage converter assembly 1 can convert the DC voltage provided on the input side into a single-phase or multi-phase AC voltage. The embodiment shown in Figure 1 with a three-phase AC voltage serves merely as an example and does not represent a limitation of the present invention.

[0042] The voltage converter arrangement 1 can comprise a half-bridge H1, H2, H3 for each connection, i.e. each phase of the electrical load 3. Each half-bridge H1, H2, H3 comprises two switching elements, in particular semiconductor switching elements M1 to M6. For each half-bridge H1, H2, H3, an upper switching element M1, M3, M5 is arranged between a positive connection point 11a of the input connection 11 and a node point K1, K2, K3 of the respective half-bridge H1, H2, H3. Furthermore, a second, lower switching element M2, M4, M6 is arranged between the respective node point K1, K2, K3 of the respective half-bridge H1, H2, H3 and a negative connection point 11b. The node points K1, K2, K3 are connected to corresponding connection points 12a, 12b, 12c. By appropriately controlling the switching elements M1 to M6, a desired output voltage can be provided at the output terminal 12 from the DC voltage provided on the input side.

[0043] Furthermore, in the voltage converter arrangement 1, a half-bridge H1 is designed such that it can be operated as a synchronous converter. For this purpose, an inductance L is provided between the node K1 of the corresponding half-bridge H1 and an output point A. By suitably controlling the switching elements M1, M2 in this half-bridge H1, an auxiliary voltage, in particular an auxiliary DC voltage, can thus be provided at the output point A. For this purpose, the two switching elements M1, M2 of the corresponding half-bridge H1 are closed alternately. However, since the basic operation of a synchronous converter is considered to be known, a more detailed description of the clocking of the switching elements M1, M2 for synchronous converter operation is omitted here.

[0044] For controlling the switching elements M1 to M6 in the half-bridges H1 to H3, as well as possibly other components, a control device (not explicitly shown in the figures for the sake of simplicity) can be provided, for example.

[0045] If the half-bridge H1 designed as a synchronous converter is to be operated as a synchronous converter, any additional half-bridges H2, H3 that may be present are adjusted during this operating mode in such a way that all switching elements M3, M4, M5, M6 are open during synchronous converter operation.

[0046] In the half-bridge H1, which is designed as a synchronous converter, a switching element S can also be provided in addition to the inductance L between the output point A and the node K1. In this way, the output point A can be electrically separated from the corresponding half-bridge H1, in particular the node K1 of this half-bridge H1, if the half-bridge is not to be operated as a synchronous converter.

[0047] The DC voltage provided at the output point A of the half-bridge H1 designed as a synchronous converter can, for example, be used to supply at least some of the components of the voltage converter arrangement 1 with electrical energy if a primary energy supply fails. In particular, the auxiliary voltage provided at the output point A can be used to operate the discharge circuit 6. Furthermore, the auxiliary voltage provided at the output point A can also be used to provide electrical energy for driving the semiconductor switching elements M1, M2 of the half-bridge H1 designed as a synchronous converter. During operation of the half-bridge H1 as a synchronous converter, the electrical energy required for this can be provided, on the one hand, by the input-side DC voltage source 2.On the other hand, for example, when the isolating switch 4 is open, the electrical energy still stored in the intermediate circuit capacitor 5 can also be used to provide the auxiliary voltage at the output point A of the synchronous converter.

[0048] Figure 2 shows a schematic representation of a basic circuit diagram of the half-bridge H1 designed as a synchronous converter in a voltage converter arrangement 1 according to one embodiment. As shown again in detail in Figure 2, an inductance L is arranged between the node K1, at which the upper switching element M1 and the lower switching element M2 are connected to one another. The two semiconductor switching elements M1, M2, together with this inductance L, thus form the actual core of the synchronous converter. Furthermore, a switching element S and a diode D are provided between the inductance L and the output point A. The switching element S can be used to separate the output point A from the node K1 if the half-bridge is not to be operated as a synchronous converter. The diode D is used to rectify the electrical voltage.

[0049] Furthermore, a capacitor C can be provided at the output point A before or after the diode D to stabilize the auxiliary voltage at the output point A.

[0050] Furthermore, an overvoltage protection component, for example, a Zener diode ZD, can be provided. The overvoltage protection component can, for example, be provided between a reference potential and a point before or after the diode D. This ensures that the auxiliary voltage at the output point A is limited to an electrical voltage that is safe for the components connected to the output point A.

[0051] Figure 3 shows a flowchart underlying a method for operating a voltage converter arrangement 1 according to one embodiment. The voltage converter arrangement 1 can, in particular, be the voltage converter arrangement 1 previously described in connection with Figures 1 and 2. Thus, all statements made previously in connection with Figures 1 and 2 also apply to the method described below. Analogously, any components or parts that may be required to implement the method described below can also be provided in the previously described embodiments of the voltage converter arrangement 1.

[0052] The method for operating the voltage converter arrangement 1 can comprise a step S1 in which all half-bridges of the voltage converter are operated to convert a DC voltage provided at the input terminal 11 into a further voltage and to provide this further voltage at the output terminal 12. In particular, the half-bridge H1 designed as a synchronous converter can also be operated to convert the DC voltage provided at the input terminal 11 into a further voltage.

[0053] Alternatively, the half-bridge H1 configured as a synchronous converter can be operated as a synchronous converter in a step S2. The switching elements M1 and M2 of the half-bridge H1 configured as a synchronous converter are controlled to generate an auxiliary voltage from the electrical DC voltage provided at the input terminal 11 and to provide it at the output point A. During operation of the half-bridge H1 as a synchronous converter, all switching elements M3 to M6 of any additional half-bridges H2, H3 are open.

[0054] Furthermore, during operation of the half-bridge H1 as a synchronous converter, the switching element S between the inductance L and the output point A is closed. If, however, the voltage converter arrangement 1 is operated such that the electrical DC voltage provided at the input terminal 11 is converted into another DC voltage to be provided at the output terminal 12, the switching element S between the inductance L and the output point A is open.

[0055] In summary, the present invention relates to a

[0056] A voltage converter arrangement with one or more half-bridges. At least one of the half-bridges is designed so that it can also be operated as a synchronous converter. In this way, the half-bridge operated as a synchronous converter can be used to provide an auxiliary DC voltage when needed.

Claims

Claims 1. Voltage converter arrangement (1), with: an input terminal (11) which is designed to be connected to a DC voltage source (2); at least one half-bridge (H1, H2, H3), wherein each half-bridge (H1, H2, H3) comprises a first semiconductor switching element (M1, M3, M5) and a second semiconductor switching element, the first semiconductor switching element (M1, M3, M5) is arranged between a positive connection point (11a) of the input terminal (11) and a node point (K1, K2, K3) of the respective half-bridge (H1, H2, H3), and the second semiconductor switching element (M2, M4, M6) is arranged between the node point (K1, K2, K3) of the respective half-bridge (H1, H2, H3) and a negative connection point (11b) of the input terminal (11); an output terminal (12), wherein each node point (K1, K2, K3) of the at least one half-bridge (H1) (H1, H2, H3) is electrically coupled to a connection point (12a, 12b, 12c) of the output terminal (12);wherein one of the at least one half-bridge (H1) is designed as a synchronous converter; 2. Voltage converter arrangement (1) according to claim 1, wherein the half-bridge (H1) designed as a synchronous converter comprises an inductance (L) and a switching element (S) which are arranged in series between the node point (K1) of the half-bridge (H1) designed as a synchronous converter and an output point (A) of the synchronous converter.

3. Voltage converter arrangement (1) according to claim 1 or 2, with a control device which is designed to, in a first operating mode, to control first and second semiconductor switching elements (M1 - M6) of the voltage converter arrangement (1) for a voltage conversion between the input terminal (11) and the output terminal (12), and in a second operating mode to control the first and second semiconductor switching elements (M1, M2) of the half-bridge (H1) designed as a synchronous converter for a voltage conversion from the input terminal (11) to the output point (A) of the synchronous converter.

4. Voltage converter arrangement (1) according to claim 3, wherein the voltage converter arrangement (1) comprises a half-bridge (H1) which is designed as a synchronous converter, and at least one further half-bridge (H2, H3), wherein the control device is designed to open the switching elements (M3 - M6) of the further half-bridge (H2, H3) when the half-bridge (H1) designed as the synchronous converter is operated as a synchronous converter.

5. Voltage converter arrangement (1) according to one of claims 1 to 4, wherein the half-bridge (H1) designed as a synchronous converter comprises an overvoltage protection element, in particular a Zener diode (ZD), which is arranged between the output point (A) of the synchronous converter and a reference potential.

6. A control circuit for an electric drive system, comprising: a voltage converter arrangement (1) according to one of claims 1 to 5; wherein the half-bridge (H1) designed as a synchronous converter is designed to provide electrical energy for controlling driver circuits of the at least one half-bridge (H1, H2, H3).

7. Control circuit according to claim 6, comprising a discharge circuit (6) designed to actively discharge an intermediate circuit capacitor (5); wherein the half-bridge (H1) designed as a synchronous converter is designed to provide electrical energy for operation of the discharge circuit (6).

8. Electric drive system, comprising: an electric machine (3); and Voltage converter arrangement (1) according to one of claims 1 to 5; wherein each connection point (12a, 12b, 12c) of the output terminal (12) of the voltage converter arrangement is connected to a terminal of the electrical machine (3).

9. A method for operating a voltage converter arrangement (1) according to one of claims 1 to 7, comprising the steps: Operating (S1) the half-bridge (H1) designed as a synchronous converter as a voltage converter for converting a DC voltage provided at the input terminal (11) into a further voltage and providing the further voltage at a connection point (12a, 12b, 12c) of the output terminal (12); and Operating (S2) the half-bridge (H1) designed as a synchronous converter as a synchronous converter, for converting a DC voltage provided at the input terminal (11) into an auxiliary voltage and providing the auxiliary voltage at an output point (A) of the synchronous converter.

10. The method according to claim 9, comprising a step of opening all semiconductor switching elements (M3 - M6) in further half-bridges (H2, H3) of the voltage converter arrangement which are not designed as synchronous converters, if the half-bridge (H1) designed as a synchronous converter is operated as a synchronous converter.

Images