Charging device, and method for operating the charging device

Abstract

The invention relates to a charging device for a vehicle, the input side of the charging device (500) comprising an input terminal unit (100) for connecting a single-phase or multiphase alternating voltage and a PFC stage (200) for providing a direct voltage at an intermediate terminal (300), the PFC stage (200) comprising a half-bridge (210, 220, 230) for each phase of the n-phases, a first switching element (S1) being connected on one side to the positive ends of the half-bridges and on the other side to the positive intermediate terminal (310) and being designed to enable or interrupt a current flow between the positive ends of the half-bridges and the positive intermediate terminal (310) via the first switching element (S1).

Description

[0001] Description

[0002] title

[0003] Charger and method for operating the charger

[0004] The invention relates to a charger and a method for operating the charger. Furthermore, the invention relates to a powertrain with a charger, a vehicle with a powertrain, a computer program, and a computer-readable storage medium.

[0005] State of the art

[0006] Chargers, for example in electric vehicles or hybrid vehicles, are used to recharge batteries, preferably accumulators or traction batteries, from an electrical energy source, preferably an external AC source or the public AC grid. To do this, the charger converts a sinusoidal alternating current from the external energy source into a direct current. With single-phase alternating current, the power pulses at twice the frequency of the alternating current.

[0007] Chargers preferably have two-stage power electronics. A first stage, the so-called power factor correction stage, or PFC stage, converts the sinusoidal input voltage from the AC mains into a DC voltage. A second stage consists of a DC-DC converter or DC / DC converter, which ensures galvanic isolation via a transformer and adjusts the voltage levels. The output voltage and / or output current for charging the battery is preferably adjusted using an electrical circuit and a control system. An intermediate capacitor is arranged between the two stages, which buffers the power pulsation at twice the frequency of the AC current of the energy source. This intermediate circuit is typically implemented using at least one electrolytic capacitor.These topologies enable the maintenance of a nearly sinusoidal input current on the grid side to meet grid-side standards, galvanic isolation between the grid and the vehicle to meet safety requirements, and the provision of a constant DC output current on the battery side to minimize the load on the battery during charging.

[0008] In an electric vehicle, the battery is also connected to an inverter to supply the electric drive motor with power. A DC-DC converter is connected in parallel to the inverter to supply a low-voltage network or the vehicle's on-board electrical system to supply the control units with power. At the start of the charging process, the charger is connected to the sinusoidal input voltage from the AC voltage network, or the AC low-voltage network, via a PFC stage. The PFC stage is connected or interconnected on the output side to the intermediate capacitor, which is part of a voltage intermediate circuit. The voltage intermediate circuit is discharged when connected to the AC low-voltage network. Due to its low impedance, a high inrush current is generated when the AC low-voltage network is switched on, which charges the voltage intermediate circuit.To prevent grid-side disturbances or the destruction of power electronics components, such as fuse blowouts due to overcurrent, this inrush current must be limited. A common implementation for inrush current limitation is to use pre-charging resistors in the connecting lines between the AC mains and the PFC stage, which are bridged by relays during normal operation. A corresponding inrush current must be limited in each connecting line of the PFC stage. This requires a large number of pre-charging resistors and relays. Therefore, there is a need for a simple and compact solution that enables charging of the intermediate capacitor with fewer components.

[0009] Disclosure of the invention

[0010] A charger for a vehicle is provided, the charger comprising on the input side a single- or multi-phase, n-phase, where n is an integer greater than or equal to 1, preferably three-phase, input connection unit for connecting an n-phase AC voltage and a PFC stage for providing a DC voltage at a two-pole intermediate connection. The intermediate connection comprises a positive intermediate connection and a negative intermediate connection. The PFC stage comprises an n-th half-bridge for each of the n-phases. Each half-bridge comprises a series circuit with a high-side switch and a low-side switch. A center tap between the high-side switch and the low-side switch of a half-bridge can be connected via a respective choke to one of the n-input connections of the n-phase input connection unit via a respective n-th connecting line.Thus, for example, the center tap of the first half-bridge can be connected to the first input terminal via the first choke and the first connection line. Thus, for example, the center tap of the second half-bridge can be connected to the second input terminal via the second choke and the second connection line, and so on. The n-type half-bridges are connected in parallel. The high-side switches are connected to the positive ends of the half-bridges and the low-side switches are connected to the negative ends of the half-bridges. The negative ends of the half-bridges are connected to the negative intermediate terminal. An intermediate capacitor is connected between the positive intermediate terminal and the negative intermediate terminal. This intermediate capacitor is part of the voltage intermediate circuit. A first switching element is connected to the positive ends of the half-bridges on the one hand and to the positive intermediate terminal on the other.The first switching element is designed to enable or interrupt a current flow between the positive ends of the half-bridges and the positive intermediate terminal via the first switching element. For clarity, the wording that the first switching element is connected, on the one hand, to the positive ends of the half-bridges and, on the other hand, to the positive intermediate terminal is preferably used below. It is preferably equivalent that the first switching element is connected, on the one hand, to the negative ends of the half-bridges and, on the other hand, to the negative intermediate terminal. This preferably arises from the fact that the terms “positive” and “negative” are used merely as different terms and can be replaced with a list, such as “first” and “second”, with equivalent meaning.Advantageously, a circuit is provided for a charger with a multi-phase AC voltage input, in which it is possible for an inrush current to flow across all phases of the AC voltage input and through the P FC stage to charge the intermediate capacitor. By means of the first switching element, the inrush current can be interrupted by the first switching element following the half-bridges. Preferably, a pre-charging resistor is arranged parallel to the first switching element, which enables a limited charging current to bypass the first switching element to charge the intermediate capacitor. Preferably, the first switching element is opened only after the intermediate capacitor has been charged, thus enabling a low-impedance connection between the positive ends of the half-bridges and the positive intermediate connection.Advantageously, the otherwise necessary n-type pre-charging resistors, preferably each with a bridging switching element, between the individual input terminals and the chokes of the P FC stage are omitted. The pre-charging resistor is preferably a PTC thermistor or PTC resistor, which is used to limit the inrush current. The inrush current for charging the intermediate capacitor preferably flows from at least one of the input terminals via the P FC stage and the pre-charging resistor into the intermediate capacitor. The pre-charging resistor reduces the inrush current and thus prevents an overcurrent. Preferably, to avoid losses in the series resistor, it is bridged by closing the first switching element when the intermediate capacitor is substantially charged.

[0011] An external energy source is preferably a single- or multi-phase, preferably three-phase AC voltage network, preferably the public low-voltage grid. In a North American region or Japanese region, this is preferably a single-phase AC voltage network with 120 or 240 volts. In a Chinese or European region, this is preferably a three-phase AC voltage network with approximately 230 volts. For charging operation of the charger, the charger is preferably connected to a corresponding AC voltage network via the n-phase input connection unit or connected to the corresponding AC voltage. The n-phase input connection unit preferably comprises a neutral conductor connection for connecting a neutral conductor of the AC voltage network to be connected. A battery to be charged is preferably an accumulator or a traction battery, by means of which energy an electric drive train of a vehicle is operated.A rectification circuit is preferably a rectifier for converting alternating current into direct current. A high-side switch or a low-side switch of a semiconductor bridge is preferably a power semiconductor switch comprising an intrinsic diode, preferably an IGBT or MOSFET, preferably based on Si, SiC, or GaN technology. The phrase "connecting, for example, a center tap to a connecting line" preferably means connecting, contacting, or connecting the components by means of an electrically conductive line or a galvanic connection. The phrase "blocking, preventing, decoupling, or preventing a current flow" means breaking an electrically conductive line or connection.Preferably, the term "switched" is used synonymously with "electrically connected," where "switchably connected" means that an electrical connection can be established or broken, preferably by means of a switch or switching element. Preferably, the term "arranged" is used to define the position of an electrical component, preferably a switch or switching element, within the circuit topology, which includes an electrical connection with the adjacent electrical components.

[0012] In one embodiment, in order to charge the intermediate capacitor before the start of a charging process, the first switching element is opened so that no charging current flows from the positive ends of the half-bridges via the first switching element to the positive intermediate terminal.

[0013] Advantageously, a control of the first switching element is provided that prevents a current flow through the first switching element when charging the intermediate capacitor. Since the current flows through the precharging resistor connected in parallel with the first switching element, no high inrush current or overcurrent occurs through the phases of the input connection unit.

[0014] In one embodiment, the intermediate capacitor is charged until the voltage across the intermediate capacitor equals or exceeds a predeterminable voltage value. The opening of the first switching element for the charging process of the intermediate capacitor is continued until the voltage across the intermediate capacitor equals or exceeds a predeterminable voltage value. For this purpose, the voltage across the intermediate capacitor is determined using a detection unit or a measuring device and compared with the predeterminable voltage value. This predeterminable voltage value is specified depending on the voltage applied to at least one of the input terminals or corresponds to it.To determine the predeterminable value, the voltage present at one of the input terminals is preferably determined using a suitable detection unit or measuring device and preferably specified as a voltage value depending on the magnitude of the maximum amplitude. Alternatively, the voltage value is preferably specified depending on the connected AC voltage or the region in which the charger is operated, or preferably read from a characteristic map and specified.

[0015] Alternatively, in another embodiment, the intermediate capacitor is charged until the alternating current through at least one of the connecting lines falls below a predeterminable alternating current value. The predeterminable alternating current value is preferably 100 mA. The predeterminable alternating current value is preferably set so low that no overcurrent occurs during subsequent control of the first switching element such that a charging current is conducted from the positive ends of the half-bridges via the first switching element to the positive intermediate connection. For this purpose, the alternating current is preferably determined during the charging of the intermediate capacitor using an alternating current measuring unit. For this purpose, the alternating current measuring unit is preferably arranged at least between one of the input connections and the intermediate connection.

[0016] Advantageously, a control system for the charger is provided that prevents a high inrush current through the phases of the input connection unit for connecting the multiphase AC voltage. In another embodiment, to provide electrical energy at the intermediate connection for a charging process, an AC voltage provided at the input connection unit is provided via the PFC stage at least partially as a DC voltage at the positive intermediate connection and at the negative intermediate connection, wherein the first switching element is closed so that a charging current flows from the positive ends of the half-bridges via the first switching element to the positive intermediate connection.

[0017] During a charging process, the charger converts electrical energy provided at the input connection unit, the provided alternating voltage or the provided alternating current, into a charging voltage for charging a battery, preferably for charging a vehicle battery. For this purpose, the charger has a two-stage design. The first stage, the PFC stage, converts the sinusoidal input voltage from the alternating voltage network into a direct voltage at the voltage intermediate circuit. The second stage, a downstream DC-DC converter, which preferably ensures galvanic isolation via a transformer, adjusts the voltage levels, and on the output side, the charging voltage and charging current for charging the battery are provided by means of a circuit and a control system.

[0018] Advantageously, a topology is provided which enables a DC voltage to be provided at the intermediate terminal for a charging process, the energy for this being provided by an external energy source which provides a multi-phase AC voltage at the input terminal unit.

[0019] In another embodiment, the intermediate capacitor is designed as a series circuit comprising a first capacitor and a second capacitor.

[0020] The intermediate capacitor is preferably designed as a series connection of a first and a second capacitor. The capacitance of the first capacitor and the second capacitor is preferably the same. A neutral conductor, preferably switchable, is preferably connected to a center tap between the first and the second capacitor for connection to a corresponding contact of the input connection unit. A neutral conductor is preferably provided for operation of the charger with asymmetrical loading. An asymmetrical load preferably occurs when operating with a 2-phase network or with asymmetrical loading when operating with a 3-phase network, i.e. two-phase or three-phase alternating voltage. In these cases, a compensating current flows back into the alternating voltage network connected on the input side via the neutral conductor.

[0021] Advantageously, a suitable circuit topology for connecting a neutral conductor is provided.

[0022] Furthermore, the invention relates to a drive train of a vehicle with a charger as described above, wherein the drive train comprises, in particular, a traction battery, an inverter, and / or an electric machine. Advantageously, a drive train of an electric vehicle with a charger with a simplified circuit topology is provided.

[0023] Furthermore, the invention relates to a vehicle with a drive train as described above.

[0024] Advantageously, a vehicle is provided with a charger having a simplified circuit topology.

[0025] Furthermore, the invention relates to a method for operating a charger as presented above, comprising the step of controlling the first switching element as well as the high-side and low-side switches of the half-bridges to provide electrical energy to the intermediate capacitor.

[0026] By controlling the first switching element and the switches of the half-bridges, the alternating voltage applied to the input terminal is first used to charge the intermediate capacitor and then permanently converted into a direct voltage to supply the connected DC-DC converter of the charger to generate the charging voltage for the battery to be charged. Advantageously, a method is provided that enables the provision of a direct voltage at the voltage intermediate circuit. Furthermore, the invention relates to a computer program comprising instructions that, when executed by a computer, cause the computer to execute the described method.

[0027] Furthermore, the invention relates to a computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the described method.

[0028] It is understood that the features, characteristics and advantages of the charger apply accordingly to the method or the powertrain and the vehicle and vice versa.

[0029] Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the accompanying drawings.

[0030] Short description of the drawing

[0031] In the following, the invention will be explained in more detail with reference to some figures, which show:

[0032] Figure 1 is a schematic representation of an embodiment of a circuit topology for a charger known from the prior art

[0033] Figure 2 is a schematic representation of an embodiment of a circuit topology for a charger,

[0034] Figure 3 shows a schematic representation of a vehicle with a drive train with a charger,

[0035] Figure 4 is a schematic flow diagram for a method for operating a charger

[0036] Embodiments of the invention

[0037] Figure 1 shows a charger 500, preferably for a vehicle. The charger 500 comprises, on the input side, an input connection unit 100 for connecting a three-phase alternating voltage (illustrated by way of example), and a PFC stage 200 for providing a direct voltage at an intermediate terminal 300. The PFC stage 200 of the charger 500 comprises a first 210, a second 220, and a third 230 half-bridge. The first, second and third half-bridges 210, 220, 230 each comprise a series circuit with a high-side switch 211, 213, 215 and a low-side switch 212, 214, 216. A center tap between the high-side switch and the low-side switch of a half-bridge can be connected via a first, second and third choke 202, 204, 206 to a first, second and third input terminal LI, L2, L3 of the input connection unit 100 via a first, second and third connection line 110, 120, 130.Thus, the center tap of the first half-bridge 210 is connectable to the first input terminal L1 via the first choke 202 and the first connecting line 110. Thus, the center tap of the second half-bridge 220 is connectable to the second input terminal L2 via the second choke 204 and the second connecting line 120. Thus, the center tap of the third half-bridge 230 is connectable to the third input terminal L3 via the third choke 206 and the third connecting line 130. The half-bridges 210, 220, 230 are connected in parallel. Their ends are connected to the two-pole intermediate terminal 300. The high-side switches are connected to a positive intermediate terminal 310 and the low-side switches to a negative intermediate terminal 320. A DC-DC converter 450 is preferably connected to the intermediate terminal 300.The DC voltage at the intermediate connection 300, which is present on the input side of the DC-DC converter 450, is preferably converted into a charging voltage for charging a battery 470, preferably a traction battery or high-voltage battery, that can be connected to the output side of the DC-DC converter 450. Preferably, a further DC-DC converter 460, preferably a step-down converter, is connected in parallel to the battery 470 to convert the charging voltage into a low-voltage voltage for charging a low-voltage battery 462 and for supplying a vehicle's electrical system to power the vehicle's control units. The low-voltage battery 462, as well as preferably further low-voltage consumers 480, are connected to the vehicle's electrical system. The further DC-DC converter 460 is preferably a bidirectional DC-DC converter.Preferably, the additional DC-DC converter 460 can be used to precharge the high-voltage intermediate circuit before the battery 470 is connected to the charger 500. The high-voltage intermediate circuit is connected to the output side of the DC-DC converter 450.

[0038] Starting with the charger 500 shown in Figure 1, the charger 500 according to the invention shown in Figure 2 comprises a single- or multi-phase, an n-phase input connection unit 100 for connecting a multi-phase alternating voltage with n phases, where n is greater than or equal to 1. A three-phase input connection unit for connecting a single- to three-phase alternating voltage is shown as an example. The n-type half-bridges 210, 220, 230 are connected in parallel. The high-side switches of the half-bridges are connected to the positive ends of the half-bridges, and the low-side switches of the half-bridges are connected to the negative ends of the half-bridges. The negative ends of the half-bridges are connected to the negative intermediate terminal 320. A first switching element S1 is connected, on the one hand, to the positive ends of the half-bridges and, on the other hand, to the positive intermediate terminal 310.It is designed to enable or interrupt a current flow between the positive ends of the half-bridges and the positive intermediate terminal 310 via the first switching element S1. Preferably, a precharging resistor, preferably a switchable resistor, a PTC thermistor, or PTC resistors, is connected in parallel to the first switching element S1 so that a starting current or inrush current decays and is limited when an AC voltage is connected to the input terminal unit 100 before the first switching element S1 is closed. An intermediate capacitor CZ is connected in parallel to the half-bridges 210, 220, 230. An intermediate capacitor CZ is connected between the positive intermediate terminal 310 and the negative intermediate terminal 320. The intermediate capacitor CZ is preferably replaced by a series circuit comprising a first C1 and a second C2 capacitor (not shown).The second connecting line 120 is preferably divided into a first part of the second connecting line 120_l and a second part of the second connecting line 120_2. For this purpose, a second switching element S2 is preferably provided, which is arranged between the first part of the second connecting line 120_l and the second part of the second connecting line 120_2. The second switching element S2 is preferably configured to conduct a charging current from the second input terminal L2 via the first part and the second part of the second connecting line 120_l, 120_2 to the second choke 204 or to conduct a charging current from the first connecting line 110 via the second part of the second connecting line 120_2 to the second choke 204. To implement this function, the second switching element S2 is preferably designed as a changeover contact.Due to the design of the second switching element as a second changeover contact, a short circuit between the first connecting line and the first part of the second connecting line is preferably prevented. A short circuit between the first input connection and the second input connection would preferably be possible by means of an incorrectly controlled simple switching element. This error case during control can be reliably excluded by means of the second changeover contact. Preferably, a switching element corresponding to the second switching element and its arrangement is also installed in further phases in addition to the first and second phases of a P FC stage. Advantageously, when a single-phase external energy source is connected, the charging current is distributed over several phases by means of the second and further switching elements in order to load the individual components of the P FC stage more evenly.Preferably, a current sensor is arranged in series with each of the chokes to determine the current through the respective choke 202, 204, 206 (not shown). Depending on the determined currents, the high-side switches and the low-side switches as well as the switching elements are preferably controlled to implement the desired operating modes. Preferably, a voltage sensor (V) is arranged between the positive and the negative intermediate terminal 310, 320 to determine or measure the voltage at the intermediate capacitor. Depending on the determined voltage, the high-side switches and the low-side switches as well as the switching elements are preferably controlled to implement the desired operating modes. Preferably, the negative intermediate terminal 320 is connected to ground GND. Preferably, GND is an internal voltage potential.Preferably, the voltage at the intermediate capacitor between the positive intermediate terminal 310 and the negative intermediate terminal 320 is measured or determined. Preferably, the voltage at the input terminal is measured and determined against a neutral conductor terminal (not shown). The switching elements are preferably provided as semiconductor switch components (IGBTs or MOSFETs, based on Si, SiC, or GaN) or as contactors or relays.

[0039] Figure 3 shows a schematically illustrated vehicle 700 with a drive train 600 and a charger 500. The vehicle 700 is shown here only as an example with four wheels, although the invention can be used equally in any vehicle with any number of wheels on land, on water, and in the air. The drive train 600 shown as an example comprises at least one charger 500. Furthermore, the drive train preferably comprises a battery 470, an inverter 472, and / or an electric machine 474.

[0040] Figure 4 shows a schematic flowchart for a method 800 for operating a charger 500. Method 800 begins with step 805. In step 810, the first switching element S1 as well as the high-side and low-side switches of half-bridges 210, 220, 230 are controlled to provide electrical energy to the intermediate capacitor CZ. The method ends with step 815.

Claims

Charger for a vehicle, wherein the charger (500) comprises on the input side an input connection unit (100) for connecting a single-phase or multi-phase alternating voltage with n-phases, where n is greater than or equal to 1, and a PFC stage (200) for providing a direct voltage at a two-pole intermediate connection (300), wherein the PFC stage (200) comprises a half-bridge (210, 220, 230) for each phase of the n-phases, wherein a half-bridge (210, 220, 230) each comprises a series circuit with a high-side switch (211, 213, 215) and a low-side switch (212, 214, 216), wherein a center tap is connected between the high-side switch and the low-side switch of the half-bridge via a respective choke (202, 204, 206) with each one of the n-input terminals (LI, L2, L3) of the input connection unit (100) via an n-th connection line (110, 120, 130), wherein the n-half bridges (210, 220,230) are connected in parallel, and wherein the high-side switches are connected to the positive ends of the half-bridges and the low-side switches are connected to the negative ends of the half-bridges, wherein the negative ends of the half-bridges are connected to the negative intermediate terminal (320), wherein an intermediate capacitor (CZ) is connected between the positive intermediate terminal (310) and the negative intermediate terminal (320), characterized in that a first switching element (S1) is connected on the one hand to the positive ends of the half-bridges and on the other hand to the positive intermediate terminal (310) and is configured to enable or interrupt a current flow between the positive ends of the half-bridges and the positive intermediate terminal (310) via the first switching element (S1). Charger according to claim 1, wherein for charging the intermediate capacitor (CZ) before the start of a charging process, the first switching element (S1) is opened so that no charging current, flows from the positive ends of the half-bridges via the first switching element (S1) to the positive intermediate terminal (310). Charger according to claim 2, wherein the intermediate capacitor (CZ) is charged until the voltage at the intermediate capacitor (CZ) exceeds a predeterminable voltage value. Charger according to one of the preceding claims, wherein, in order to provide electrical energy at the intermediate terminal (300) for a charging process, an alternating voltage provided at the input terminal unit (100) is provided via the PFC stage (200) at least partially as a direct voltage at the positive intermediate terminal (310) and at the negative intermediate terminal (320), wherein the first switching element (S1) is closed such that a charging current flows from the positive ends of the half-bridges via the first switching element (S1) to the positive intermediate terminal (310).Charger according to one of the preceding claims, wherein the intermediate capacitor (CZ) is designed as a series circuit comprising a first capacitor (CI) and a second capacitor (C2). Drive train (600) of a vehicle (700) with a charger (500) according to one of the preceding claims, wherein the drive train (600) in particular comprises a traction battery (470), an inverter (472) and / or an electric machine (474). Vehicle (700) with a drive train (600) according to claim 6. Method (800) for operating a charger according to one of claims 1 to 5, comprising the step:. Controlling (810) the first switching element (Sl) as well as the high-side and low-side switches of the half-bridges (210, 220, 230) to provide electrical energy to the intermediate capacitor (CZ).

9. A computer program comprising instructions which, when executed by a computer, cause the computer to perform the method (800) according to claim 8.

10. A computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to perform the method (800) according to claim 8.

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