DC-DC voltage converter, electric vehicle and method for operating DC-DC voltage converter

Abstract

The invention relates to a DC voltage converter having three DC voltage connections. The DC voltage converter can exchange electrical energy between the three DC voltage connections in almost any manner. The DC voltage converter comprises an oscillation circuit for resonant operation. In addition, a combination of an H-bridge circuit and a buck chopper is provided at at least one DC voltage converter connection.

Description

Technical Field

[0001] The invention relates to a DC voltage converter and an electric vehicle having such a DC voltage converter. The invention also relates to a method for operating a DC voltage converter. In particular, the invention relates to a DC voltage converter having three DC voltage connections. Background Art

[0002] The onboard power system of a vehicle that is fully or at least partially electrically driven usually comprises a high-voltage power system and a low-voltage power system. The high-voltage power system usually has a DC voltage in the range of several hundred volts. The low-voltage power system usually has a significantly smaller DC voltage in the range of 12 to 14, 24 or 48 volts. Generally speaking, the electric drive system of such a vehicle and other loads with high power consumption as necessary are fed by the high-voltage power system. The low-voltage power system usually feeds loads such as, for example, lighting devices, control devices, brake and steering actuators or entertainment systems of the vehicle.

[0003] The high-voltage power grid and the low-voltage power grid can be coupled to each other, for example, by means of a DC voltage converter. With the aid of such a DC voltage converter, electrical energy can be exchanged between the high-voltage power grid and the low-voltage power grid. In this way, for example, electrical energy can be supplied from a traction battery in the high-voltage power grid to an electrical load in the low-voltage power grid by means of electrical energy.

[0004] For example, laid-open patent application DE 10 2014 210 283 A1 describes a method for operating a vehicle electrical system having at least two voltage levels with different rated voltages.

[0005] Furthermore, an additional voltage converter may be provided in such an electric vehicle, which converts the voltage at the charging connection of the vehicle into a DC voltage which is suitable for charging a traction battery of the electric vehicle. Summary of the invention

[0006] The invention provides a DC voltage converter, an electric vehicle and a method for operating a DC voltage converter having the features of the independent claims. Further advantageous embodiments are the subject matter of the dependent claims.

[0007] Therefore provide:

[0008] A DC voltage converter having a transformer, a first H-bridge circuit, a second H-bridge circuit, a DC voltage converter circuit and an oscillating circuit. The transformer comprises a primary winding, a first secondary winding and a second secondary winding. The first H-bridge circuit is connected to a first DC voltage connection at an external connection. The intermediate connection of the first H-bridge circuit is electrically coupled to the primary winding of the transformer. Here, the first oscillating circuit is electrically arranged between the intermediate connection of the first H-bridge circuit and the primary winding of the transformer. The second H-bridge circuit is connected to a second DC voltage connection at an external connection. The intermediate connection of the second H-bridge circuit is electrically coupled to the first secondary winding of the transformer. The voltage converter circuit comprises six semiconductor switching elements and an inductor. Here, the first semiconductor switching element is arranged between a first node and a first intermediate connection. The second semiconductor switching element is arranged between the first intermediate connection and the first external connection. The third semiconductor switching element is arranged between the second node and the second intermediate connection. The fourth semiconductor switching element is arranged between the second intermediate connection and the first external connection. The fifth switching element is arranged between the second external connection and the first node. The sixth switching element is arranged between the second external connection and the second node. The first external connection of the voltage converter circuit is electrically connected to the first connection point of the third DC voltage connection. The inductor is arranged between the second external connection of the voltage converter circuit and the second connection point of the third DC voltage connection. The first intermediate connection and the second intermediate connection of the voltage converter circuit are each electrically connected to a connection of the second secondary winding of the transformer.

[0009] Also available:

[0010] An electric vehicle having a high-voltage power grid, a low-voltage power grid and a DC voltage converter according to the present invention. In this case, a second DC voltage connection of the DC voltage converter is electrically coupled to the high-voltage onboard power grid of the electric vehicle. A third DC voltage connection of the DC voltage converter is electrically coupled to the low-voltage onboard power grid of the electric vehicle. In addition, the first DC voltage connection of the DC voltage converter can be designed to be connected to a charging connection or a charging circuit of the electric vehicle.

[0011] Finally provided:

[0012] A method for operating a DC voltage converter according to the present invention, wherein the method can respectively perform one of the following steps. In the method, in a first operating mode, electrical energy can be transmitted from a first DC voltage connection to a second DC voltage connection. In a second operating mode, electrical energy can be transmitted from a second DC voltage connection to a third DC voltage connection. In a third operating mode, electrical energy can be transmitted from a third DC voltage connection to a second DC voltage connection. In a fourth operating mode, electrical energy can be transmitted from a second DC voltage connection to a first DC voltage connection and a third DC voltage connection. In a fifth operating mode, electrical energy can be transmitted from a first DC voltage connection to a second DC voltage connection and a third DC voltage connection. In addition, in a sixth operating mode, electrical energy can be transmitted from a second DC voltage connection to a first DC voltage connection. In this case, in the first and sixth operating modes, the fifth and sixth switching elements of the DC voltage converter circuit can be disconnected. In the second and third operating modes, the fifth and sixth switching elements of the voltage converter circuit can be closed. In the fourth and fifth operating modes, the fifth and sixth switching elements of the voltage converter circuit can be controlled as step-down choppers.

[0013] Advantages of the present invention

[0014] The invention is based on the knowledge that, in conventional electric vehicles, a plurality of DC voltage converters can be provided, if necessary. For example, electrical energy can be exchanged between a high-voltage onboard power supply and a low-voltage onboard power supply by means of a DC voltage converter. Furthermore, a further DC voltage converter can also be provided between an external energy source and the internal onboard power supply. This implies considerable hardware expenditure and the costs associated therewith.

[0015] Therefore, the idea of ​​the present invention is to provide a DC voltage converter that can realize the exchange of electrical energy between more than two connections. It is particularly desirable to realize a cost-effective and effective DC voltage converter for energy exchange between more than two DC voltage connections.

[0016] According to the present invention, a DC voltage converter with three DC voltage connectors is provided. Here, electrical energy can be exchanged between the DC voltage connectors in almost any configuration. For example, the first DC voltage connector can be configured to be connected to an external energy source, such as a charging connector of an electric vehicle. At the charging connector, a DC voltage can be provided directly, or as an alternative, the provided AC power can be rectified by means of a rectifier and then the rectified voltage can be provided at the first DC voltage connector. The second DC voltage connector can be designed, for example, to be connected to the high-voltage onboard power grid of an electric vehicle. Such a high-voltage onboard voltage can include, for example, a traction battery and an electric drive system and, if necessary, other loads. The high-voltage onboard power grid usually has a voltage of hundreds of volts, such as 400V or 800V. The third DC voltage connector of the rectifier can be designed, for example, to be connected to the low-voltage onboard power grid of an electric vehicle. In such a low-voltage onboard power grid, for example, electrical loads, such as sensors, actuators, control devices, components of comfort functions, entertainment systems, etc. can be provided. In addition, an electric energy storage device in the form of a rechargeable battery can also be provided in such a low-voltage onboard power grid. The low-voltage onboard power supply system can have a voltage that is much lower than the voltage in the high-voltage onboard power supply system. For example, the voltage in the low-voltage onboard power supply system can be 12 to 14V, 24V or 48V.

[0017] The half-bridge circuit of the rectifier can include, for example, two half-bridges each having two semiconductor switching elements. The semiconductor switching element can be, for example, a MOSFET or a bipolar transistor (IGBT) with an insulated gate connection. The half-bridges each include two semiconductor switching elements connected in series. The two semiconductor switching elements are electrically connected to each other at the middle connection. The corresponding other connection, which is referred to here as the external connection, is connected to the corresponding connection point of the corresponding DC voltage connection. The middle connection is connected to the connection of the corresponding winding of the transformer either directly or via an oscillating circuit.

[0018] The resonant circuit can include, for example, a coil or inductor and a capacitor or capacitance connected in series. As an alternative, for example, an inductor can also be provided between an intermediate terminal and a corresponding terminal of a winding of a transformer, and a capacitor can be provided between another intermediate terminal and a terminal of a winding of a transformer corresponding to the intermediate terminal. In addition, any other configuration of the resonant circuit is of course also possible. If necessary, the resonant circuit can also be formed only by a capacitor or an inductor.

[0019] The voltage converter circuit arranged between the second secondary winding and the third current and voltage connection includes, in addition to the components of the H bridge, two further switching elements (fifth and sixth switching elements) and an inductor. These additional components enable the functionality of a step-down converter (Buck Converter).

[0020] It is thus possible to adjust the voltage at the third DC voltage connection in a suitable manner by means of the components of the step-down chopper when transmitting electrical energy to the third DC voltage connection.

[0021] As a result, a transmission of electrical energy between the three DC voltage connections can be achieved in an efficient manner, wherein the voltage at the individual connections can be set or adjusted in a targeted manner.

[0022] According to one embodiment, the first semiconductor switch element and the fifth semiconductor switch element are complementary semiconductor switch elements. Similarly, the second semiconductor switch element and the sixth semiconductor switch element are complementary semiconductor switch elements. The first, second, third and fourth semiconductor switch elements can be identical or at least the same semiconductor switch elements. Complementary semiconductor switch elements relative to n-channel transistors are, for example, p-channel transistors and vice versa. In particular, complementary semiconductor switch elements have opposite cut-off directions or conduction directions in the disconnected state. The semiconductor switch element can be, for example, a MOSFET or a bipolar transistor (IGBT) with an insulated gate terminal. In principle, a hybrid form can also be conceivable, in which, for example, the first to fourth semiconductor switch elements are made as IGBTs and the fifth to sixth semiconductor switch elements are made as MOSFETs.

[0023] According to one embodiment, the first H-bridge circuit and the second H-bridge circuit each include four semiconductor switching elements. The four semiconductor switching elements are especially manufactured in the form of two half bridges. Here, the first semiconductor switching element is always arranged between the first external terminal and the first intermediate terminal of the corresponding H-bridge circuit. The second semiconductor switching element is arranged between the first external terminal and the second intermediate terminal of the corresponding H-bridge circuit. The third semiconductor switching element is always arranged between the second external terminal and the first intermediate terminal of the corresponding H-bridge circuit. The fourth semiconductor switching element is always arranged between the second external terminal and the second intermediate terminal of the corresponding H-bridge circuit.

[0024] According to one embodiment, the DC voltage converter includes a second oscillating circuit. The second oscillating circuit is electrically arranged between the middle joint of the second H-bridge circuit and the first secondary winding of the transformer. Similar to the first oscillating circuit, the second oscillating circuit can also include a capacitor and an inductor. For example, a series circuit consisting of a capacitor and an inductor can be arranged between the middle joint of the second H-bridge circuit and the corresponding joint of the first secondary winding of the transformer. As an alternative, it is also possible to arrange a capacitor between the first middle joint of the second H-bridge circuit and the corresponding joint of the first secondary winding of the transformer and to arrange an inductor between the second middle joint and the joint of the first secondary winding of the transformer corresponding to this second middle joint. As an alternative, the second oscillating circuit can also only include a capacitor, which is arranged between the middle joint of the second H-bridge circuit and the corresponding joint of the first secondary winding of the transformer.

[0025] According to one embodiment, the DC voltage converter comprises a control device. The control device is designed to control the semiconductor switching elements of the first H-bridge circuit, the second H-bridge circuit and the voltage converter circuit in the DC voltage converter. In particular, the control can be performed, for example, by means of a pulse width modulated control signal. The control device can be designed to adjust the frequency and / or phase of the AC voltage occurring on the primary winding and / or the first secondary winding of the transformer in resonant operation.

[0026] According to a further specific embodiment, the control device may be designed to actuate the fifth and / or sixth semiconductor switching element of the voltage converter circuit in a buck chopper mode.

[0027] According to one embodiment, the DC voltage converter is designed to transmit electrical energy from the first DC voltage connection to the second DC voltage connection in a first operating mode. For example, electrical energy can be transmitted from the energy source connected to the first DC voltage connection of the electric vehicle to its traction battery connected to the second DC voltage connection in order to charge the traction battery. In this case, the DC voltage converter can be operated in a resonant operation corresponding to the resonant frequency of the first oscillating circuit. In addition, the DC voltage converter can be designed to transmit electrical energy from the second DC voltage connection to the third DC voltage connection in a second operating mode. If a second oscillating circuit is provided between the second H-bridge circuit and the first secondary winding of the transformer, the DC voltage converter can also be operated in a resonant operating mode. In this second operating mode, for example, electrical energy can be transmitted from the traction battery connected to the second DC voltage connection of the electric vehicle to the low-voltage onboard power grid of the electric vehicle connected to the third DC voltage connection. In this case, the fifth and sixth switching elements of the voltage converter circuit can be closed. In addition, the DC voltage converter can be designed to transmit electrical energy from the third DC voltage connection to the second DC voltage connection in the third operating mode. The fifth and sixth switching elements of this voltage converter circuit can be closed. In this third operating mode, for example, electric energy can be transmitted from the low-voltage onboard power grid of the electric vehicle to the high-voltage onboard power grid of the electric vehicle at the second DC voltage connection, so as to charge the intermediate circuit in the high-voltage onboard power grid. In addition, the DC voltage converter can be designed to transmit electric energy from the second DC voltage connection to the first DC voltage connection and the third DC voltage connection at the same time in the fourth operating mode. Here, in this fourth operating mode, the fifth and sixth switching elements of the voltage converter circuit can be controlled together with the inductor of the voltage converter circuit as a step-down chopper. In this way, it is possible to specifically adjust the voltage at not only the first DC voltage connection but also the voltage at the third DC voltage connection to a preset target value. In addition, the DC voltage converter can be designed to transmit electric energy from the first DC voltage connection to the second DC voltage connection and simultaneously to the third DC voltage connection in the fifth operating mode. Here, the fifth and / or sixth switching elements of the voltage converter circuit can be controlled as a step-down chopper. Finally, the DC voltage converter can be designed to transfer electrical energy from the second DC power connection to the first DC voltage connection in a sixth operating mode. In this case, both the fifth and the sixth switching element of the voltage converter circuit are closed.

[0028] The above-mentioned designs and improvements can be combined with each other arbitrarily as long as it makes sense. Other designs, improvements and implementations of the present invention also include combinations of features described above or below with respect to the embodiments of the present invention that are not explicitly mentioned. In particular, those skilled in the art will also add individual aspects as improvements or supplements to the corresponding basic forms of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Other features and advantages of the present invention are explained below with the aid of the accompanying drawings.

[0030] Figure 1 A schematic diagram showing a principle circuit diagram for a DC voltage converter according to one embodiment is shown;

[0031] Figure 2 A schematic diagram showing a schematic diagram of a principle diagram of an H-bridge circuit in a DC voltage converter according to one embodiment;

[0032] Figure 3 A schematic diagram showing a schematic diagram of a principle diagram of a DC voltage converter according to another embodiment; and

[0033] Figure 4 A flow chart is shown as a basis for a method for operating a DC converter according to one specific embodiment. DETAILED DESCRIPTION

[0034] Figure 1 A schematic diagram of a principle circuit diagram of a DC voltage converter 1 according to an embodiment is shown. The DC voltage converter 1 includes three DC voltage connections G1, G2 and G3. If such a DC voltage converter 1 is used, for example, in an electric vehicle, an external energy source, such as a charging station, is connected to the first DC voltage connection G1. If this charging station already provides a DC voltage, the provided charging voltage can be provided directly, if necessary, at the first DC voltage connection G1 through a suitable disconnect switch. If a single-phase or multi-phase AC voltage is provided by an external energy source, this AC voltage can be converted into a DC voltage by a rectifier or other suitable charging circuit 100 if necessary and the DC voltage is provided at the first DC voltage connection G1.

[0035] For example, a high-voltage onboard power supply 200 of an electric vehicle can be connected to the second DC voltage connection G2. Such a high-voltage onboard power supply 200 can include, for example, a traction battery, an electric drive system or other arbitrary electrical loads. The high-voltage onboard power supply usually has a voltage of several hundred volts, for example, 350 to 400V or 800V.

[0036] For example, a low-voltage onboard power supply 300 of an electric vehicle can be connected to the third DC voltage connection G3. For example, electrical loads such as control devices, sensors, actuators, components for comfort functions in the electric vehicle, entertainment systems, etc. can be connected to this low-voltage onboard power supply 300. Electrical energy storage devices such as lead-acid batteries, etc. can also be arranged in this low-voltage onboard power supply 300. The low-voltage onboard power supply 300 usually has a voltage that is significantly lower than the voltage in the high-voltage onboard power supply 200. For example, the voltage in the low-voltage onboard power supply 300 can be 12 to 14V, 24V or 48V.

[0037] The DC voltage converter 1 is designed to exchange electrical energy between three DC voltage connections G1, G2 and G3. A transformer TR is provided in the DC voltage converter 1. In this way, the individual DC voltage connections G1, G2 and G3 can be electrically separated from each other.

[0038] The transformer TR comprises a primary winding 11, a first secondary winding 12 and a second secondary winding 13. In addition, the DC voltage converter 1 comprises a first H-bridge circuit H1, a second H-bridge circuit H2 and a voltage converter circuit H3. The principle structure of the H-bridge circuits H1 and H2 will be explained in detail below.

[0039] Two external terminals A11, A12 of the first H-bridge circuit H1 are electrically connected to corresponding connection points of the first DC voltage terminal G1. Two intermediate terminals M11, M12 of the first H-bridge circuit H1 are connected to two terminals of the primary winding 11 via a first resonant circuit S1.

[0040] The first resonant circuit S1 can include, for example, a first capacitor C1 and a first inductor I1. For example, the first capacitor C1 can be arranged between the first middle terminal M11 of the first H-bridge circuit H1 and the corresponding terminal of the primary winding 11. In addition, the first inductor I1 can be arranged between the second middle terminal M12 of the first half-bridge H1 and another terminal of the primary winding 11. As an alternative, it is also possible to arrange a series circuit consisting of the first capacitor C1 and the first inductor I1 between the middle terminals M11, M12 of the first half-bridge H1 and the terminals of the primary winding 11. In addition, other suitable arrangements consisting of structural elements for the resonance of the first resonant circuit S1 are also possible if necessary.

[0041] The second H-bridge circuit H2 is electrically connected with two external connections to corresponding connection points of the second DC voltage connection G2. The two central connections of the second H-bridge circuit H2 are connected to two connections of the first secondary winding 12 of the transformer TR. If necessary, further resonant components can be arranged between the connection points of the first secondary winding 12 of the transformer TR and the central connections of the second H-bridge circuit H2. This will be explained in more detail below.

[0042] A voltage converter circuit H3 is arranged between the third DC voltage connection G3 and the second secondary winding 13 of the transformer TR. The voltage converter circuit H3 comprises six semiconductor switching elements T1 to T6 and an inductor L. If necessary, it is also possible to use the (parasitic) inductance of the second secondary winding 13 of the transformer TR in addition to or as an alternative to this discrete inductor.

[0043] The first semiconductor switching element T1 is arranged between the first node K1 of the voltage converter circuit H3 and the first intermediate terminal M1. The second switching element T2 is arranged between the first intermediate terminal M1 of the voltage converter circuit H3 and the first external terminal A1. The third switching element T3 is arranged between the second node K2 of the voltage converter circuit H3 and the second intermediate terminal M2. The fourth switching element T4 is arranged between the second intermediate terminal M2 and the first external terminal A1.

[0044] Furthermore, a fifth semiconductor switching element T5 is arranged between the second external connection A2 of the voltage converter circuit H3 and the first node K1. Finally, a sixth semiconductor switching element T6 is arranged between the second external connection A2 and the second node K2.

[0045] The first external connection A1 is electrically connected to a first connection point of the third DC voltage connection G3. An inductor L is arranged between a second external connection A2 of the voltage converter circuit H3 and a second connection point of the DC voltage connection G3.

[0046] In this way, a combination of the third H-bridge circuit 31 and the step-down chopper 32 is formed by the voltage converter circuit H3 .

[0047] The switching elements T1 to T6 of the voltage converter circuit H3 and the switching elements of the first half-bridge circuit H1 and the second half-bridge circuit H2 can be controlled in a suitable manner by the control device 20. In this way, electrical energy can be exchanged between the DC voltage connections G1, G2 and G3 in almost any manner. In order to regulate the energy transmission, current and / or voltage sensors (not shown) can be provided in the DC voltage converter 1 if necessary. The sensor values ​​of these current or voltage sensors can be provided at the control device 20. The control device 20 then generates control signals for the switching elements in the first half-bridge circuit H1, the second half-bridge circuit H2 and the voltage converter circuit H3 using the target value presetting for the energy transmission and the output voltage to be set. These control signals can be provided at the corresponding switching elements by suitable driver stages if necessary.

[0048] Figure 2The schematic diagram shows a basic circuit diagram of a half-bridge circuit as can be used, for example, as a first half-bridge circuit H1 or a second half-bridge circuit H2 in the rectifier 1 according to the invention. Even though embodiments are described below in conjunction with the first half-bridge circuit H1, these embodiments also apply analogously to the second half-bridge circuit H2.

[0049] As in Figure 2 As shown in , the first half-bridge circuit H1 includes two half-bridges each having two semiconductor switching elements T11 to T14 connected in series. The first semiconductor switching element T11 is arranged between the first external terminal A11 and the first intermediate terminal M11. The second semiconductor switching element T12 is arranged between the first intermediate terminal M11 and the second external terminal A12. The third semiconductor switching element T13 is arranged between the first external terminal A11 and the second intermediate terminal M12. The fourth semiconductor switching element T14 is arranged between the second intermediate terminal M12 and the second external terminal A12. The two external terminals A11 and A12 are connected to the corresponding terminals of the primary winding 11 of the transformer TR through the first oscillating circuit S1.

[0050] The second half-bridge circuit H2 is constructed similarly to the circuit principle described above with four semiconductor switching elements T21 to T24. The semiconductor switching element T21 is therefore arranged between the external terminals A21 and A22 and the central terminals M21 and M22.

[0051] Figure 3 A schematic diagram of a principle circuit diagram of a DC voltage converter 1 according to another embodiment is shown. Here, all previously described circuit diagrams are applicable, as long as they can be applied. Figure 1 and 2 Explanation given. Figure 3 The DC voltage converter 1 of the embodiment of the present invention is particularly distinguished in that a second oscillating circuit S2 is provided between the first secondary winding 12 of the transformer TR and the second half-bridge circuit H2. This oscillating circuit can include, for example, a second capacitor C2 and a second inductor I2. For example, a series circuit consisting of the second capacitor C2 and the second inductor I2 can be provided between the connection point of the first secondary winding 12 of the transformer TR and the middle connection of the second half-bridge circuit H2. As an alternative, the second capacitor C2 can also be provided between the connection of the first secondary winding 12 of the transformer TR and the first middle connection of the second half-bridge H2, and the second inductor I2 can be provided between the other connection of the first secondary winding 12 of the transformer TR and the second middle connection of the second half-bridge H2. If necessary, it is possible for only one capacitor C2 to be provided as the second oscillating circuit S2 between the connection of the first secondary winding 12 of the transformer TR and the middle connection of the second half-bridge circuit H2.

[0052] In order to transmit electrical energy between the DC voltage connections G1, G2 and G3, the switching elements of the first half-bridge circuit H1 and the second half-bridge circuit H2 can be controlled in such a way that an AC voltage is applied to the windings of the transformer TR, wherein the frequency and / or phase of these AC voltages can be adjusted taking into account the resonant frequency of the first resonant circuit S1 and / or the second resonant circuit S2. In this way, a resonant operating mode can be set in the DC voltage converter 1. However, since the basic principle of such a resonant operation is considered to be known, a more detailed explanation is omitted here.

[0053] Different operating modes are possible for exchanging electrical energy between the DC voltage connections G1 , G2 and G3 . Some exemplary operating modes are explained in more detail below with reference to the method according to the invention for operating the DC voltage converter 1 .

[0054] Figure 4 A flow chart is shown which can serve as a basis for a method for operating a DC voltage converter 1 , in particular the DC voltage converter 1 described above, according to one specific embodiment.

[0055] In order to operate the DC voltage converter 1, the control device 20 can control the switching elements in the H-bridge circuits H1, H2 and / or in the voltage converter circuit H3 in a suitable manner. For this purpose, for example, pulse width modulated control can be performed in order to set the desired voltage at the corresponding primary or secondary winding 11, 12, 13 in terms of amplitude, frequency and phase.

[0056] In a first operating mode B1, for example, electrical energy can be transmitted from the first DC voltage connection G1 to the second DC voltage connection G2. In this case, the fifth switching element T5 and the sixth switching element T6 of the voltage converter circuit H3 can be disconnected. In this way, the third DC voltage connection G3 is electrically separated from the second secondary winding 13 of the transformer TR. In order to transmit energy from the first DC voltage connection G1 to the second DC voltage connection G2, an AC voltage can be generated in a resonant operating mode, the frequency and / or phase of which is adjusted taking into account the resonant frequency of the first resonant circuit S1. In such a first operating mode B1, for example, electrical energy can be transmitted from an energy source connected to the first DC voltage connection G1 to a traction battery connected to the second DC voltage connection G2, in order to charge the traction battery, for example.

[0057] In the second operating mode B2, for example, electrical energy can be transferred from the second DC voltage connection G2 to the third DC voltage connection G3. Thus, for example, electrical energy can be transferred from a traction battery in the high-voltage network of the electric vehicle to the low-voltage network of the electric vehicle. If a second resonant circuit S2 is provided between the second half-bridge circuit H2 and the first secondary winding 12 of the transformer TR, a resonant operation can also be set here taking into account the resonant frequency of the second resonant circuit S2. In order to transfer electrical energy from the second DC voltage connection G2 to the third DC voltage connection G3, both the fifth switching element T5 and the sixth switching element T6 are closed.

[0058] In the third operating mode B3, electrical energy can be transmitted from the third DC voltage connection G3 to the second DC voltage connection G2. As a result, for example, an intermediate circuit in a high-voltage onboard power supply connected to the second DC voltage connection G2 can be charged. In this case, both the fifth switching element T5 and the sixth switching element T6 are closed. In order to transmit electrical energy from the third DC voltage connection G3 to the second DC voltage connection G2, the switching elements T1-T4 in the H-bridge circuit 31 of the voltage converter circuit H3 can be controlled, for example, according to the dual active bridge principle. Since this switching principle is also considered to be known, no further details will be discussed here.

[0059] In the fourth operating mode B4, for example, electrical energy can be transmitted from the second DC voltage connection G2 to the first DC voltage connection G1 and simultaneously to the third DC voltage connection G3. In this case, the DC voltage converter 1 is operated in the resonant operating mode so that the DC voltage to be set is applied to the first DC voltage connection G1. The fifth switching element T5 and the sixth switching element T6 and the inductor L of the DC voltage converter circuit H3 form a step-down chopper 32. Thus, the control device 20 can set the voltage on the third DC voltage connection G3 according to a preset target value by appropriately controlling the fifth switching element T5 and the sixth switching element T6 of this step-down chopper 32.

[0060] In the fifth operating mode B5, electrical energy can be transmitted from the first DC voltage connection G1 to the second DC voltage connection G2 and simultaneously from the first DC voltage connection G1 to the third DC voltage connection G3. In this case, in the resonant operating mode, the voltage at the second DC voltage connection G2 is first set according to the target value specification. In addition, the voltage at the third DC voltage connection G3 can also be set here by appropriately controlling the fifth switching element T5 and the sixth switching element T6 in the step-down chopper circuit 32 of the voltage converter circuit H3.

[0061] Finally, in the sixth operating mode B6, electrical energy can be transmitted from the second DC voltage connection G2 to the first DC voltage connection G1 and simultaneously to the third DC voltage connection G3. If necessary, a resonant operating mode can also be selected. In this case, the fifth switching element T5 and the sixth switching element T6 of the voltage converter circuit H3 are open.

[0062] In summary, the invention relates to a DC voltage converter having three DC voltage connections. In this case, electrical energy can be exchanged between the three DC voltage connections in almost any manner. The DC voltage converter comprises an oscillating circuit for resonant operation. In addition, a combination of an H-bridge circuit and a step-down chopper is provided at at least one DC voltage converter connection.

Claims

1. A DC voltage converter (1), comprising: A transformer (TR) having a primary winding (11), a first secondary winding (12) and a second secondary winding (13); a first H-bridge circuit (H1) which is connected to a first DC voltage terminal (G1) at external terminals (A11, A12) and is electrically coupled to a primary winding (11) of a transformer (TR) at intermediate terminals (M11, M12); a first oscillating circuit (S1) electrically arranged between the intermediate terminals (M11, M12) of the first H-bridge circuit (H1) and the primary winding (11) of the transformer (TR); a second H-bridge circuit (H2) which is connected to the second DC voltage terminal (G2) at the external terminal and is electrically coupled to the first secondary winding (12) of the transformer (TR) at the central terminal; and A voltage converter circuit (H3), wherein a first semiconductor switching element (T1) is arranged between a first node (K1) and a first intermediate terminal (M1), a second semiconductor switching element (T2) is arranged between the first intermediate terminal (M1) and a first external terminal (A1), a third semiconductor switching element (T3) is arranged between a second connection point (K2) and a second intermediate terminal (M2), a fourth semiconductor switching element (T4) is arranged between the second intermediate terminal (M2) and the first external terminal (A2), a fifth switching element (T5) is arranged between the second external terminal (A2) and the first node (K1), and a sixth switching element (T6) is arranged between the second external terminal (A2) and the second node (K2), and The first external connection (A1) is electrically connected to a first connection point of a third DC voltage connection (G3), an inductor (L) is arranged between a second external connection (A2) and a second connection point of the third DC voltage connection (G3), and the first intermediate connection (M1) and the second intermediate connection (M2) are respectively electrically connected to the connection of the second secondary winding (13) of the transformer (TR).

2. A DC voltage converter (1) according to claim 1, wherein the first semiconductor switching element (T1) and the fifth semiconductor switching element (T5) of the voltage converter circuit (H3) are complementary semiconductor switching elements, and the second semiconductor switching element (T2) and the sixth semiconductor switching element (T6) of the voltage converter circuit (H3) are complementary semiconductor switching elements.

3. The DC voltage converter (1) according to claim 1 or 2, wherein the first H-bridge circuit (H1) and the second H-bridge circuit (H2) respectively comprise a first semiconductor switching element (T11, T21) arranged between a first external terminal (A11, A21) and a first intermediate terminal (M11, M21) of the corresponding H-bridge circuit (H1, H2), and a first semiconductor switching element (T11, T21) arranged between the first external terminal (A11, A21) and the second intermediate terminal (M11, M21) of the corresponding H-bridge circuit (H1, H2). 12, M22), a second semiconductor switching element (T12, T22) arranged between the second external terminal (A12, A22) of the corresponding H-bridge circuit (H1, H2) and the first intermediate terminal (M11, M21), and a fourth semiconductor switching element (T14, T24) arranged between the second external terminal (A12, A22) of the corresponding H-bridge circuit (H1, H2) and the second intermediate terminal (M12, M22).

4. A DC voltage converter (1) according to any one of claims 1 to 3, comprising a second oscillating circuit (S2), which is electrically arranged between the intermediate terminals (M21, M22) of the second H-bridge circuit (H2) and the first secondary winding (12) of the transformer (TR).

5. The DC voltage converter (1) according to claim 1 , comprising a control device (20) which is designed to actuate semiconductor switching elements (T11-T14, T21-T24, T1-T6) of the first H-bridge circuit (H1), the second H-bridge circuit (H2) and the voltage converter circuit (H3), The control device (20) is designed to adjust the frequency and / or phase of an AC voltage occurring at the primary winding (11) and / or at one of the secondary windings (12, 13) during resonant operation.

6. The DC voltage connection (1) according to claim 5, wherein the control device (20) is designed to actuate the fifth and / or sixth semiconductor switching element (T5, T6) of the voltage converter circuit (A1) in a step-down chopper mode.

7. The DC voltage converter (1) according to any one of claims 1 to 6, wherein the DC voltage converter (1) is designed to: In a first operating mode, electrical energy is transmitted from a first DC voltage connection (G1) to a second DC voltage connection (G2), In a second operating mode, electrical energy is transmitted from the second DC voltage connection (G2) to the third DC voltage connection (G3), In a third operating mode, electrical energy is transmitted from the third DC voltage connection (G3) to the second DC voltage connection (G2), In a fourth operating mode, electrical energy is transmitted from the second DC voltage connection (G2) to the first DC voltage connection (G1) and the third DC voltage connection (G3), In a fifth operating mode, electrical energy is transmitted from the first DC voltage connection (G1) to the second DC voltage connection (G2) and the third DC voltage connection (G3), and In a sixth operating mode, electrical energy is transmitted from the second DC voltage connection (G3) to the first DC voltage connection (B1); The fifth and sixth switching elements (T5, T6) of the voltage converter circuit (H3) are open in the first and sixth operating modes, closed in the second and third operating modes, and driven as step-down converters in the fourth and fifth operating modes.

8. An electric vehicle having High voltage on-board power grid (200); A low voltage on-board electrical network (300); and A DC voltage converter (1) according to any one of claims 1 to 7; wherein the second DC voltage connector (G2) of the DC voltage converter (1) is electrically coupled to the high-voltage onboard power grid (2) of the electric vehicle; and The third DC voltage connection (G3) of the DC voltage converter (1) is electrically coupled to the low-voltage onboard power system (300) of the electric vehicle.

9. The electric vehicle according to claim 8 comprises a rectifier (100), which is designed to be coupled to a single-phase or multi-phase AC voltage source at an AC voltage input and is electrically coupled to a first DC voltage connection (G1) of the DC voltage converter (1) at a DC voltage output.

10. A method for operating a DC voltage converter (1) according to any one of claims 1 to 7, wherein one of the following steps is respectively performed when operating the DC voltage converter (1): In a first operating mode, electrical energy is transmitted (B1) from a first DC voltage connection (G1) to a second DC voltage connection (G2); In a second operating mode, electrical energy is transmitted (B2) from the second DC voltage connection (G2) to the third DC voltage connection (G3); In a third operating mode, electrical energy is transmitted (B3) from the third DC voltage connection (G3) to the second DC voltage connection (G2); In a fourth operating mode, electrical energy is transmitted (B4) from the second DC voltage connection (G2) to the first DC voltage connection (G1) and the third DC voltage connection (G3); In a fifth operating mode, electrical energy is transmitted (B5) from the first DC voltage connection (G1) to the second DC voltage connection (G2) and the third DC voltage connection (G3); or In a sixth operating mode, electrical energy is transmitted (B6) from the second DC voltage connection (G2) to the first DC voltage connection (G1); The fifth and sixth switching elements (T5, T6) of the voltage converter circuit (H3) are open in the first and sixth operating modes, closed in the second and third operating modes, and driven as step-down converters in the fourth and fifth operating modes.

Images