Charging device and method for charging an energy store

Abstract

The invention relates to a charging device (100b) for charging an energy store, wherein: the charging device has an AC-DC converter (110) with terminals (130.1, 130.2, 130.3, 130.4) for multiple phases (a, b, c) of an AC voltage and for a neutral conductor (N); the AC-DC converter (110) has half-bridges (H1, H2, H3); each of the half-bridges can be connected on the input side to a terminal of a phase; the half-bridges are each connected on the output side jointly to a positive (110+) and negative intermediate point (110-); the charging device has two DC link capacitors (C1, C2); a central tap between the two DC link capacitors is connected to the terminal for the neutral conductor; the charging device has a plurality of DC-DC buck converters (B1, B2, Bn), a positive and a negative DC voltage terminal (120+, 120-); the DC-DC buck converters are each connected on the input side to the positive and the negative intermediate point; the DC-DC buck converters can each be connected on the output side to the positive and the negative DC voltage terminal; the charging device has a first switch (S1); a selected one of the half-bridges can be connected on the input side via the first switch, in a first position (j1), to the corresponding terminal of the corresponding phase and, in a second position (j2), to the terminal (130.4) for the neutral conductor.

Description

[0001] Description

[0002] title

[0003] Charging device and method for charging a

[0004] The present invention relates to a charging device, in particular an on-board charging device for an electrically operated vehicle, for charging an energy storage device, an electric vehicle and a method for charging an energy storage device.

[0005] Background of the invention

[0006] Electric vehicles are trending in the automotive industry because they use cleaner energy and can deliver better performance than fossil-fuel-powered vehicles. On-board charging devices can be used to charge energy storage devices in electric vehicles.

[0007] Disclosure of the invention

[0008] According to the invention, a charging device for charging an energy storage device, an electric vehicle, and a method for charging an energy storage device are proposed, each having the features of the independent patent claims. Advantageous embodiments are the subject of the dependent claims and the following description.

[0009] The invention relates to the charging of energy storage devices in general and to the charging of energy storage devices in electric vehicles in particular. Electric vehicles (EVs) are a trend in the automotive industry because they consume cleaner energy and can achieve better performance than fossil fuel-powered vehicles. Furthermore, there is a general trend toward increasing electrification in automotive technology. In the following, an electric vehicle is understood to mean a vehicle with an electric drive (electric motor), preferably with a purely electric drive, but also as a hybrid drive.

[0010] For charging a vehicle's energy storage device, such as a battery (typically a high-voltage battery pack), so-called on-board chargers (OBCs) can be considered. These can generally be provided, for example, as on-board interfaces between the energy storage device and a drive inverter. These are widely used in electric vehicles due to their simple installation and low cost. To achieve high efficiency with a small size and minimal space requirement, so-called non-isolated (transformerless) on-board chargers are a particularly promising solution.

[0011] Within the scope of the present invention, a charging device, in particular an on-board charging device (or also referred to as on-board charger, OBC) for an electrically powered vehicle, is proposed for charging an energy storage device from an alternating voltage.

[0012] The charging device features an AC-DC converter with connections for several phases of the alternating current and a neutral conductor. Typically, three phases are provided, meaning there are four connections in total. These connections can be connected directly to a charging plug or charging socket, or indirectly via the drive inverter.

[0013] At this point it should be mentioned that when reference is made here or elsewhere to a connection or interconnection or to two components being connected or interconnected, this should be understood to mean in particular an electrical or electrically conductive connection or interconnection. The AC-DC converter has a plurality of half-bridges, each of the plurality of half-bridges being assigned to one of the plurality of phases, so for example three half-bridges can be provided. Depending on the type of concept, e.g. two-level or three-level concept, the half-bridges can be designed in different ways. In a simple variant, for the two-level concept, each half-bridge can have, for example, two switches, a high-side switch and a low-side switch. Suitable switches can be semiconductor switching elements such as MOSFETs, IGBTs and the like, but also electromechanical switches.

[0014] A center tap between the two switches can be connected, or connectable, to the respective phase terminal, possibly via an inductor. For the three-level concept, somewhat more complex half-bridge configurations can be provided, which are shown as examples in the figures and described in the corresponding figure description.

[0015] Each of the multiple half-bridges is connected or connectable on the input side to a respective terminal of the respective phase. In the case of a simple half-bridge with, for example, two switches, the center tap is the input terminal of the half-bridge.

[0016] In addition, the multiple half-bridges are each connected to a positive intermediate point and a negative intermediate point on the output side. In the case of a simple half-bridge with, for example, two switches, the high-side switch is connected to the positive intermediate point, and the low-side switch is connected to the negative intermediate point. These then form the input-side connections of the half-bridge.

[0017] The charging device also has two intermediate circuit capacitors connected in series between the positive and negative intermediate points, with a center tap between the two intermediate circuit capacitors being connected to the neutral conductor connection. In addition, each of the plurality of half-bridges is connected on the output side to the neutral conductor connection. The charging device also has several buck DC-DC converters (also referred to as step-down converters or DC-DC step-down converters) with a positive and a negative DC voltage connection for the energy storage device. The plurality of buck DC-DC converters are each connected on the input side to the positive intermediate point and the negative intermediate point. On the output side, the plurality of buck DC-DC converters are each connected or connectable to the positive DC voltage connection and the negative DC voltage connection.

[0018] A distinction can be made here depending on the application, for example. In one embodiment, the multiple buck DC-DC converters are connected in parallel, and the negative intermediate point is connected to the negative DC voltage terminal. There can be as many buck DC-DC converters as there are phases, for example three, but this is not mandatory. In a simple embodiment, such a buck DC-DC converter can have, for example, two switches, a high-side switch and a low-side switch. Suitable switches can be semiconductor switching elements such as MOSFETs, IGBTs and the like, but electromechanical switches can also be used.

[0019] A center tap between the two switches can be connected, or connectable, to the positive DC voltage terminal on the output side, possibly via an inductor. The two switches are connected accordingly on the input side. In addition, for function as a buck DC-DC converter, a capacitor can be provided between the negative-side input (low-side switch) and the output terminal or the positive DC voltage terminal.

[0020] In one embodiment, the multiple buck DC-DC converters are connected in series. In this case, the number does not have to correspond to the number of phases. For example, two or more buck DC-DC converters can be provided for three phases. A somewhat more complex configuration can be provided here, which is shown as an example in the figures and described in the corresponding figure description. Each of the multiple buck DC-DC converters can then be connected on the input side (then with more than two input-side connections) to the connection for the neutral conductor.

[0021] Furthermore, the charging device has a first switch, wherein a selected one of the plurality of half-bridges can be connected on the input side via the first switch, in a first position (of the first switch), to the corresponding terminal of the corresponding phase, and, in a second position (of the first switch), can be connected to a terminal for the neutral conductor.

[0022] Thus, for charging an energy storage device, in particular an energy storage device of an electric vehicle, the first switch can be moved to the first position with a multi-phase alternating voltage. However, with a single-phase alternating voltage, the first switch can be moved to the second position; in particular, the single-phase alternating voltage is connected to a terminal other than the terminal to which the selected one of the several half-bridges can be connected.

[0023] This allows the voltage across the two intermediate capacitors to be balanced with the current through the respective half-bridge or its inductance. The neutral current (current in the neutral conductor) also flows through the respective half-bridge or its inductance instead of through the two intermediate capacitors. This results in a low common-mode voltage, thus reducing the leakage current.

[0024] In one embodiment, the charging device has a second switch, wherein a selected one of the plurality of buck DC-DC converters is connectable on the output side via the second switch, in a first position (of the second switch), to the positive DC voltage terminal, and, in a second position (of the second switch), is separable therefrom.

[0025] Depending on the type or configuration of the multiple buck DC-DC converters, a third switch may also be provided. For example, if the multiple buck DC-DC converters are connected in series, the charging device may have a third switch, wherein the selected one of the multiple buck DC-DC converters can be connected to the negative DC voltage terminal via the third switch in a first position (of the third switch) and can be disconnected from the negative DC voltage terminal in a second position (of the third switch).

[0026] This allows, for charging an energy storage device, in particular an energy storage device of an electric vehicle, the second switch can be moved to the first position (closed) with a multi-phase alternating voltage, and the third switch can also be moved to the first position (closed). However, with a single-phase alternating voltage, the second switch can be moved to the second position (open), and the third switch can also be moved to the second position (open).

[0027] The respective buck DC-DC converter can thus be operated as an active power filter (APF) to reduce the voltage ripple in the DC link. If the output capacitance is high enough, the respective buck DC-DC converter can also be used as an active power filter without a second switch. This reduces the voltage ripple on the DC link capacitors without the additional cost of a second switch. This results in a low common-mode voltage and low costs. No additional capacitor is required for the active power filter function; instead, the buck DC-DC converter is used as such. This results in low costs and small volume.

[0028] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0029] The invention is illustrated schematically in the drawing using exemplary embodiments and is described below with reference to the drawing.

[0030] Brief description of the drawings Figure 1a shows schematically a charging device according to the invention in a preferred embodiment.

[0031] Figure 1b shows schematically a charging device according to the invention in a further preferred embodiment.

[0032] Figure 2 shows schematically a charging device according to the invention in a further preferred embodiment.

[0033] Figures 3a, 3b, 3c, 3d schematically show half bridges for a charging device in various preferred embodiments.

[0034] Figures 4a, 4b schematically show buck DC-DC converters for a charging device in various preferred embodiments.

[0035] Figure 5a shows schematically a charging device according to the invention in a further preferred embodiment.

[0036] Figure 5b shows schematically a charging device according to the invention in a further preferred embodiment.

[0037] Embodiment(s) of the invention

[0038] Figure 1a schematically shows a preferred embodiment of a charging device 100a according to the invention. The charging device 100a can, for example, be designed as an on-board charging device for an electrically powered vehicle and for charging an energy storage device from an alternating voltage. An alternating voltage is shown here as an example with three phases a, b, c, and a neutral conductor N. These connections are designated 130.1, 130.2, 130.3, 130.4 and are integrated, for example, into an EMI filter 130. One EMI filter 130 is typically provided in such a charging device and can be part of the charging device 100a. The charging device 100a has an AC-DC converter 110, which in turn has connections for the three phases a, b, c and the neutral conductor N. The AC-DC converter 110 in turn has a plurality of half-bridges, each of the plurality of half-bridges being assigned to one of the plurality of phases a, b, c.Accordingly, there are three half-bridges, designated H1, H2, and H3. Half-bridges H1, H2, and H3 can be constructed identically and, for example, have four terminals AH_1, AH_2, AH_3, and AH_4. However, other half-bridge variants are also conceivable, for example, having only the three terminals AH_1, AH_2, and AH_3. Details and variants of the half-bridges are shown in Figures 3a, 3b, 3c, and 3d.

[0039] Each of the several half-bridges is connected or connectable on the input side, here at terminal AH_1, to a respective terminal of the respective phase. On the output side, here at terminals AH2 and AH3, the several half-bridges are each connected together to a positive intermediate point 110+ and a negative intermediate point 110-. These intermediate points do not necessarily have to be specific points or components; rather, they are intended to explain the electrical circuitry.

[0040] In the charging device 100a, the plurality of half-bridges are also connected on the output side, at the terminal AH_4, for example, to each other and to the terminal 130.4 for the neutral conductor N.

[0041] Furthermore, the charging device 100a has two intermediate circuit capacitors C1, C2, which are connected in series between the positive intermediate point 110+ and the negative intermediate point 110-, wherein a center tap 110m between the two intermediate circuit capacitors C1, C2 is connected to the terminal 130.4 for the neutral conductor.

[0042] Furthermore, the charging device has a plurality of buck DC-DC converters, which are designated here collectively as a group with 120; the buck DC-DC converters themselves are designated here with B1, B2, Bn. In addition, the charging device 100a has a positive DC voltage connection 120+ and a negative DC voltage connection 120- for the energy storage device 150. The energy storage device 150 is shown schematically here and can be, for example, a battery. A DC voltage U can then be provided to the energy storage device, e.g. for charging. Three buck DC-DC converters are shown as an example, but there could also be only two or more than three.

[0043] Furthermore, the multiple buck DC-DC converters are each connected on the input side, at a terminal AB_2, to the positive intermediate point 110+ and, at a terminal AB_1, to the negative intermediate point 110-. Furthermore, the multiple buck DC-DC converters are each connected or connectable on the output side, at a terminal AB_3, to the positive DC voltage terminal 120+.

[0044] In the example shown of charging device 100a, the multiple buck DC-DC converters are connected in parallel, and the negative intermediate point 110 is connected to the negative DC voltage terminal 120. Terminal AB_1 serves as both the input and output terminals. Details and variants of the buck DC-DC converters are shown in Figures 4a, 4b, and 4c.

[0045] Furthermore, the charging device 100a has a first switch S1, wherein the half-bridge H1 can be connected on the input side, i.e. at the terminal H1, via the first switch S1, in a first position j1, to the corresponding terminal 130.3 of the corresponding phase c, and, in a second position j2, to the terminal 130.4 for the neutral conductor N.

[0046] Figure 1b schematically illustrates a charging device 100b according to the invention in a further preferred embodiment. Charging device 100b essentially corresponds to charging device 100a shown in Figure 1a, so reference can be made to the description therein.

[0047] However, the charging device 100b has a second switch S2, wherein the buck DC-DC converter B1 on the output side, here at the terminal AB_3, can be connected to the positive DC voltage terminal via the second switch S1 in a first position (as shown), and can be separated from it in a second position.

[0048] Thus, in order to charge the energy storage device 150, the first switch S1 can be moved to the first position j1 ​​in the case of a multi-phase alternating voltage; and the second switch S2 can also be moved to the first position, ie, closed.

[0049] However, with a single-phase alternating voltage, e.g. with only phase a, the first switch S1 can be moved to the second position j2; and the second switch S2 can also be moved to the second position, ie opened.

[0050] Thus, the voltage across the two intermediate capacitors O1, O2 can be balanced with the current through the respective half-bridge H1 and its inductance. The neutral current (current in the neutral conductor) also flows through the respective half-bridge H1 and its inductance instead of through the two intermediate capacitors O1, O2. This results in a low common-mode voltage, thus reducing the leakage current.

[0051] The buck DC-DC converter B1 can be operated as an active power filter (APF) to reduce the voltage ripple in the DC link.

[0052] If the output capacitance of the buck DC-DC converter B1 (see also Figure 4a) is high enough, the buck DC-DC converter B1 can also be used as an active power filter without a second switch—as shown in Figure 1a with the charging device 100a. Thus, the voltage ripple across the intermediate circuit capacitors C1, C2 is reduced by the second switch at no additional cost. This results in a low common-mode voltage and low costs. No additional capacitor is required for the active power filter function; rather, the buck DC-DC converter is used as such. This results in low costs and low volume.

[0053] Figure 2 schematically illustrates a charging device 200 according to the invention in a further preferred embodiment. Charging device 200 essentially corresponds to charging device 100b according to Figure 1b, so reference can be made to the description therein.

[0054] The charging device 200 also has a plurality of buck DC-DC converters, which are, however, wired differently here than in the charging device 100b according to Figure 1b, and are referred to collectively as group 220. The buck DC-DC converters themselves are designated K1, K2, Kn. The energy storage device is designated 250 and is embodied, for example, as a battery pack. A direct voltage U can then be provided to the energy storage device, e.g., for charging. Three buck DC-DC converters are shown as an example, but there could also be only two or more than three.

[0055] In addition, the multiple buck DC-DC converters are each connected on the input side, at a terminal AK_2, to the positive intermediate point 110+ and, at a terminal AK_6, to the negative intermediate point 110-. Furthermore, each of the multiple buck DC-DC converters is connected on the input side, at a terminal AK_1, to the center tap 110 m between the two intermediate circuit capacitors C1, C2 and to terminal 130.4 for the neutral conductor N.

[0056] Furthermore, the multiple buck DC-DC converters are each connected or connectable on the output side to the positive DC voltage terminal 120+ at a terminal AK_3. Likewise, the multiple buck DC-DC converters are each connected or connectable on the output side to the negative DC voltage terminal 120- at a terminal AK_5. Furthermore, the multiple buck DC-DC converters can each be connected on the output side to a center tap of the energy storage device (e.g., between two units of the battery pack) at a terminal AK_4. The charging device 200 also has a third switch S3, wherein the buck DC-DC converter K1 is connectable on the output side, here at terminal AK_5, via the third switch S3 in a first position (as shown) to the negative DC voltage terminal, and in a second position, can be disconnected from the latter.

[0057] Thus, in order to charge the energy storage device 250, with a multi-phase alternating voltage, the first switch S1 can be brought into the first position j1; and the second switch S2 and the third switch S3 can also be brought into the first position, ie, closed.

[0058] However, with a single-phase alternating voltage, e.g. with only phase a, the first switch S1 can be moved to the second position j2; and the second switch S2 and the third switch S3 can also be moved to the second position, ie opened.

[0059] Thus, the voltage across the two intermediate capacitors O1, O2 can be balanced with the current through the respective half-bridge H1 and its inductance. The neutral current (current in the neutral conductor) also flows through the respective half-bridge H1 and its inductance instead of through the two intermediate capacitors O1, O2. This results in a low common-mode voltage, thus reducing the leakage current.

[0060] The buck DC-DC converter K1 can be operated as an active power filter (APF) to reduce the voltage ripple in the DC link.

[0061] Figures 3a, 3b, 3c, 3d schematically illustrate half-bridges Ha, Hb, Hc, Hd for a charging device in various preferred embodiments. Each of the half-bridges Ha, Hb, Hc, Hd can in principle be used as one of the half-bridges H1, H2, H3 in the charging devices 100a, 100b, 200. In particular, however, the half-bridge Ha serves for a two-level concept, while the half-bridges Hb, Hc, Hd serve for a three-level concept. The half-bridge Ha has, for example, two switches 301, 302: a high-side switch 301 for the output-side terminal AH2 and a low-side switch 302 for the output-side terminal AH3. In addition, the half-bridge Ha has, for example, an inductance 303, which is connected to the input-side terminal AH_1 and the center tap between the two switches 301, 302. The switches can be, for example, MOSFETs or other semiconductor switching elements.

[0062] The half-bridge Hb comprises, for example, two switches 301, 302: a high-side switch 301 for the output-side terminal AH2 and a low-side switch 302 for the output-side terminal AH3. Furthermore, the half-bridge Hb comprises, for example, an inductor 303 connected to the input-side terminal AH_1 and the center tap between the two switches 301, 302. The switches can be, for example, MOSFETs or other semiconductor switching elements.

[0063] Furthermore, the half-bridge Hb has, for example, two additional switches 304, 305, which are connected in series to the output terminal AH_4 and the center tap between the two switches 301, 302. This allows a further voltage level to be achieved. The two switches 304, 305 can, in particular, be connected in opposite directions, so that current flow is possible (via the body diode) in one or the other direction.

[0064] The half-bridge Hc has, for example, two switches 301, 302, a high-side switch 301 for the output-side connection AH2, and a low-side switch 302 for the output-side connection AH3. A diode 311 is connected between switch 301 and connection AH2, and a diode 312 is connected between switch 302 and connection AH_3. In addition, the half-bridge Hc has, for example, an inductance 303 which is connected to the input-side connection AH_1 and the center tap between the two switches 301, 302. The switches can be, for example, MOSFETs or other semiconductor switching elements. Furthermore, the half-bridge Hc has, for example, two further diodes 313, 314 which are connected in series and between the connections AH_2, AH_3; A center tap between the two additional diodes 313, 314 is connected to the output terminal AH_4. This allows a further voltage level to be achieved.The two further diodes 313, 314 are connected in particular in such a way that a current flow is possible in one or the other direction.

[0065] The half-bridge Hd has, for example, four diodes 321, 322, 311, 312, the two diodes 321, 311 for the output-side connection AH_2, and the two diodes 322, 312 for the output-side connection AH_3. A diode 311 is connected between switch 301 and connection AH2. In addition, the half-bridge Hd has, for example, an inductance 303 which is connected to the input-side connection AH_1 and the center tap between the four diodes 321, 322, 311, 312. In addition, a switch 323 is connected between the connections AH_2 and AH_3. The switches can be, for example, a MOSFET or another semiconductor switching element.

[0066] Furthermore, the half-bridge Hd has, for example, two additional diodes 313, 314 connected in series between terminals AH_2, AH_3; a center tap between the two additional diodes 313, 314 is connected to the output terminal AH_4. This allows a further voltage level to be achieved. The diodes are specifically connected in such a way that current flow is possible in either direction.

[0067] Figures 4a, 4b schematically illustrate buck DC-DC converters B, K for a charging device in various preferred embodiments. The buck DC-DC converter B can be used as any of the buck DC-DC converters B1, B2, Bn in the charging devices 100a, 100b. The buck DC-DC converter K can be used as any of the buck DC-DC converters K1, K2, Kn in the charging device 200. In particular, however, the half-bridge Ha serves for a two-level concept, while the half-bridges Hb, Hc, Hd serve for a three-level concept. The buck DC-DC converter B has, for example, two switches 401, 402: a high-side switch 401 for the input-side terminal AB_2 and a low-side switch 402 for the input-side terminal AB_1. In addition, the buck DC-DC converter B has an inductance 403, which is connected to the output terminal AB_3 and the center tap between the two switches 401, 402. The switches can be, for example,These can be MOSFETs or other semiconductor switching elements. Buck DC-DC converter B also includes an inductor 404 connected between the input terminal AB_1 (which can also serve as the output terminal) and the output terminal AB_3.

[0068] The buck DC-DC converter K has, for example, two switches 411, 412: a high-side switch 411 for the input-side terminal AK_2 and a low-side switch 412 for the input-side terminal AK_1. Furthermore, the buck DC-DC converter K has an inductor 413 connected to the output-side terminal AK_3 and the center tap between the two switches 411, 422. Furthermore, the buck DC-DC converter K has an inductor 424 connected between the input-side terminal AK_1 and the output-side terminal AK_3.

[0069] In addition, the buck DC-DC converter K has, for example, two further switches 421, 422: a high-side switch 421 for the input-side terminal AK_1 and a low-side switch 422 for the input-side terminal AK_6. Furthermore, the buck DC-DC converter K has an inductance 423 connected to the output-side terminal AK_5 and the center tap between the two switches 421, 422. Furthermore, the buck DC-DC converter K has an inductance 424 connected between the input-side terminal AK_1 and the output-side terminal AK_5.

[0070] In addition, the input-side terminal AK_1 is also connected to an output-side terminal AK_4. The switches can be, for example, MOSFETs or other semiconductor switching elements. Figure 5a schematically shows a charging device 500a according to the invention in a further preferred embodiment. The charging device 500a corresponds to the charging device 100a according to Figure 1a, wherein the half-bridges H1, H2, H3 (which form an AC-DC converter 510) each use the half-bridge Ha according to Figure 3a. The buck-DC-DC converter B according to Figure 4a is used as the buck-DC-DC converters B1, B2, Bn. Furthermore, the charging device 500a is shown entirely as an electrical circuit, including the half-bridges and the buck-DC-DC converters.

[0071] Figure 5b schematically illustrates a charging device 500b according to the invention in a further preferred embodiment. Charging device 500b corresponds to charging device 100b according to Figure 1b, wherein the half-bridges H1, H2, H3 (which form an AC-DC converter 510) each use the half-bridge Ha according to Figure 3a. The buck-DC-DC converter B according to Figure 4a is used as the buck-DC-DC converters B1, B2, Bn. Furthermore, charging device 500b is illustrated entirely as an electrical circuit, including the half-bridges and the buck-DC-DC converters.

[0072] Figure 5a shows the concept where only the first switch S1 is used to balance the voltage across two DC link capacitors and the voltage ripple across capacitor by the AC phase current for single-phase operation. Another concept in this idea is that one phase in the buck DC-DC converter, for example B1, is used as an active power filter to compensate the voltage ripple in the DC link voltage, so that the DC link capacitor is significantly reduced. This concept can be used when the output capacitance is high enough. Figure 5b, on the other hand, shows the concept where B1 is used with the second switch S2 as an APF. The second switch S2 is open when B1 is used as an APF.

Claims

Claims 1. Charging device (100a, 100b, 200, 500a, 500b), in particular an on-board charging device for an electrically operated vehicle, for charging an energy storage device from an alternating voltage, wherein the charging device has an AC-DC converter (110) with connections (130.1, 130.2, 130.3, 130.4) for several phases (a, b, c) of the alternating voltage and a neutral conductor (N), wherein the AC-DC converter (110) has several half-bridges (H1, H2, H3, Ha, Hb, Hc, Hd), wherein each of the several half-bridges is assigned to one of the several phases, wherein each of the several half-bridges is connected or connectable on the input side to a respective connection of the respective phase, wherein the several half-bridges are each connected on the output side together with a positive intermediate point (110+) and a negative intermediate point (110-), wherein the charging device comprises two intermediate circuit capacitors (C1, C2) connected in series between the positive and the negative intermediate point (110+,110-), wherein a center tap between the two intermediate circuit capacitors is connected to the connection for the neutral conductor, wherein the charging device has a plurality of buck DC-DC converters (B, B1, B2, Bn, K), a positive and a negative DC voltage connection (120+, 120-) for the energy storage device, wherein the plurality of buck DC-DC converters are each connected on the input side to the positive intermediate point and the negative intermediate point, wherein the plurality of buck DC-DC converters are each connected or connectable on the output side to the positive DC voltage connection and the negative DC voltage connection, and, wherein the charging device has a first switch (S1), wherein a selected one of the plurality of half-bridges is connectable on the input side via the first switch, in a first position (j 1 ), to the corresponding terminal of the corresponding phase, and, in a second position (j2), is connectable to the terminal (130.4) for the neutral conductor.

2. Charging device (100b, 200, 500b) according to claim 1, which has a second switch (S2), and wherein a selected one of the plurality of buck DC-DC converters is connectable on the output side via the second switch, in a first position, to the positive DC voltage terminal, and, in a second position, is separable from the latter.

3. The charging device (100a, 100b, 500a, 500b) according to claim 1 or 2, wherein the plurality of buck DC-DC converters are connected in parallel, and wherein the negative intermediate point is connected to the negative DC voltage terminal.

4. The charging device (200) according to claim 1 or 2, wherein the plurality of buck DC-DC converters are connected in series.

5. Charging device (100a, 100b, 200, 500a, 500b) according to claim 3 and 4, wherein each of the plurality of buck DC-DC converters is further connected on the input side to the terminal for the neutral conductor (N).

6. Charging device (200) according to claim 2 and 5, which has a third switch (S3), and wherein the selected one of the plurality of buck DC-DC converters is connectable on the output side via the third switch, in a first position, to the negative DC voltage terminal, and, in a second position, is separable from the latter.

7. Charging device (100a, 100b, 200, 500a, 500b) according to one of the preceding claims, wherein each of the plurality of half-bridges is connected on the output side to the terminal (130.4) for the neutral conductor (N).

8. Charging device (100a, 100b, 200, 500a, 500b) according to one of the preceding claims, wherein each of the plurality of half-bridges has an inductance connected to the respective terminal of the phase on the input side.

9. Electric vehicle with an energy storage device (150, 250) and a charging device (100a, 100b, 200, 500a, 500b) according to one of the preceding claims, wherein the charging device is connected to the energy storage device via the positive and the negative terminal for the energy storage device.

10. A method for charging an energy storage device (150, 250), in particular an energy storage device of an electric vehicle, using a charging device (100a, 100b, 200, 500a, 500b) according to one of claims 1 to 7 or an electric vehicle according to claim 8, wherein in the case of a multi-phase alternating voltage the first switch (S1) is brought into the first position (j1), and / or wherein in the case of a single-phase alternating voltage the first switch (S1) is brought into the second position (j2), and wherein in particular the single-phase alternating voltage is connected to a terminal other than the terminal to which the selected one of the plurality of half-bridges can be connected.

11. The method according to claim 10 with reference to claim 2, wherein in the case of the multi-phase alternating voltage the second switch (S2) is brought into the first position, and / or wherein in the case of the single-phase alternating voltage the second switch (S2) is brought into the second position.

12. The method according to claim 11, with reference to claim 6, wherein in the case of the multi-phase alternating voltage the third switch (S3) is brought into the first position, and / or wherein in the case of the single-phase alternating voltage the third switch (S3) is brought into the second position.

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