Bidirectional vehicle charging circuit for generating two different voltages

Abstract

A bidirectional vehicle charging circuit (LS) has a multi-phase bridge circuit, which has a first, a second and a third half-bridge (B1-B3). A first connection (A1 ') is connected to the first and third half-bridges (B1, B3). The second connection (A2 ') is connected to at least the second and the third half-bridge (B2, B3). A control mechanism (C) controls the half bridges. The control device (C) is configured to actuate the first half-bridge (B1) in order to convert a DC voltage (DC) on the DC voltage side of the bridge circuit into a first sinusoidal signal having a negative half-wave (NH1) with a positive offset and a first amplitude; actuating the second half-bridge (B2) in order to convert the DC voltage (DC) into a second sinusoidal signal having a positive offset and a negative half-wave (NH2) of a second amplitude; and actuating the third half-bridge in order to convert the DC voltage (DC) into a rectangular voltage as an alternating rectangular voltage level having the potentials (DC +, DC-) of the DC voltage (DC). The control device (C) controls the bridge circuit in order to generate sinusoidal voltages (V1, V2) having different amplitudes at the two connections (A1 ', A2'), and also relates to an on-board electrical system having a vehicle charging circuit.

Description

Technical Field

[0001] The present invention relates to a bidirectional vehicle charging circuit for generating two different voltages. Background Art

[0002] Vehicles with an electric drive have a high-voltage battery for traction, which feeds the vehicle's drive in driving mode.

[0003] It is also known to use the energy stored in a vehicle battery to generate a voltage that can be used by external loads. A mobile energy source is generated as a further vehicle function. Furthermore, it is also known to use a vehicle-side charging circuit, via which energy is transferred from an external charging source to the battery, to generate such a voltage for external loads by designing the circuit bidirectionally. Summary of the Invention

[0004] The object of the present invention is to specify a possibility with which an AC voltage can be supplied to a load in a wide variety of ways by means of such a bidirectional charging circuit.

[0005] This object is achieved by the subject matter of the independent claims. Further characteristics, features, embodiments and advantages emerge from the dependent claims, the description and the drawings.

[0006] The bidirectional vehicle charging circuit described herein allows, in particular, the supply of AC voltage loads, such as those commonly found in North American AC power grids. It has been found that a bidirectional charging circuit can be universally used if it can generate the same two AC voltages commonly found in single-phase, three-wire power grids (e.g., 120V and 240V AC), as is the case in the United States and Canada. In such single-phase, three-wire power grids, there is a star point or neutral conductor potential and two phases offset by 180 degrees relative to each other. Both phases have an AC voltage of 120V rms relative to the neutral conductor potential. Furthermore, for loads with a high current draw, such as electric stoves, clothes dryers, welding equipment, or other power tools, it is possible to connect the load between two phases, which are supplied with a 240V rms AC voltage. Consequently, in countries with such power grids, different load classes are common, requiring different AC voltages as nominal voltages, namely, 120V and 240V rms.

[0007] The vehicle charging circuit described herein, or a corresponding onboard electrical system including such a circuit, allows for the supply of loads with different rated voltages, such as those introduced in the United States and Canada, using the vehicle's battery as an energy source. This allows the vehicle to supply power to nearly any common AC voltage load. In particular, the circuit described herein allows for the simultaneous supply of such loads, such as for operations requiring simultaneous power supply at two voltage levels. Examples include the operation of welding equipment, a power circular saw, the charging of another electric vehicle, or the operation of a power pump, which require a voltage of 240 V AC, while simultaneously supplying a rated voltage of 120 V AC to loads such as charging equipment for battery-powered tools, construction site lighting, or a radio. Loads with different rated voltages can be operated without having to swap them in or requiring separate power paths.

[0008] It is proposed that a multi-phase bridge circuit of a vehicle charging circuit be used not only for active rectification of the charging AC current but also for generating two different AC voltages in opposite directions, starting from a DC voltage, such as that provided by a traction battery. Provision is made for the first half-bridge of the bridge circuit to be used in the feedback direction (in which the circuit transfers energy from the DC voltage side to the AC voltage connection) to generate a sinusoidal signal with half-waves offset relative to one another (in terms of amplitude), the amplitude of the half-waves corresponding to the first sinusoidal voltage. The second half-bridge of the bridge circuit is used to generate a sinusoidal signal with half-waves offset relative to one another, but, unlike the operation of the first half-bridge, the half-waves correspond to sinusoidal voltages with a second amplitude. Signals with sinusoidal half-waves are referred to herein as sinusoidal signals. In the processing method provided herein, the positive and negative half-waves are offset relative to one another. If the relevant sinusoidal half-waves are not offset relative to one another, a (continuous) sinusoidal voltage is generated. The third half-bridge is used to generate the square-wave voltage. A first voltage having a first amplitude (as a continuous sinusoidal voltage) is generated between the phase potentials of the first and third half-bridges (i.e., the potentials on the AC voltage side of the bridge circuit). A second voltage having a second amplitude (as a continuous sinusoidal voltage) is generated between the phase potentials of the second and third half-bridges.

[0009] The third half-bridge is used to offset the half-waves generated by the first two half-bridges in such a way that two different sinusoidal voltages (with different amplitudes, but in particular the same frequency and phase) are generated between the third half-bridge on the one hand and the first and second half-bridges on the other hand. The third half-bridge is thus used to offset the generated half-waves differently in terms of their voltage levels, depending on their polarity. The generated half-waves, or the sinusoidal signals with offset half-waves generated by the first two half-bridges, together with the square-wave voltage of the third half-bridge, produce a substantially sinusoidal (continuous) voltage. The third half-bridge is thus used to "merge" the (at least partially) offset half-waves at zero crossings, thereby generating a continuous sinusoidal shape at these zero crossings. Consequently, the first two half-bridges only need to generate the voltage amplitude of the generated sinusoidal voltage (in the form of each half-wave) from the zero crossing to the peak voltage, and do not need to generate the positive and negative voltage amplitudes for the two half-waves of different polarity. The third half-bridge can be controlled using a simple square-wave signal because (between the third and first / second half-bridges) only one polarity is present at each zero crossing of the sinusoidal voltage. The third half-bridge thus generates a square-wave voltage. The zero crossings of the square-wave voltage correspond to the two minimum values ​​of the positive half-wave (generated by the first two half-bridges) and the maximum value of the positive half-wave that should be generated by the first two half-bridges.

[0010] The half-waves (including offset) are generated by pulse-wave modulation from the first two half-bridges. The third half-wave is generated by a simple switchover at each zero crossing. This makes it possible to easily generate a first sinusoidal AC voltage and a second sinusoidal AC voltage with different amplitudes simultaneously or at two terminals, so that loads that rely on different AC voltages can be supplied with power.

[0011] A bidirectional vehicle charging circuit is described, which has a multi-phase bridge circuit. This bridge circuit has a first, second, and third half-bridge. The half-bridges are connected to the DC voltage side, that is, to two DC voltage potentials. When the outer ends of the half-bridges are each connected to the DC voltage side or DC voltage potential, each half-bridge has a connection point between the two switches of the corresponding half-bridge. This connection point corresponds to the AC voltage side of the bridge circuit and, in particular, forms the phase potential of the half-bridge. The bridge circuit is, in particular, a B6C bridge (or BnC bridge, where n>6). The switches of the half-bridges are, in particular, semiconductor switches, such as transistors such as IGBTs or MOSFETs, in particular SiC MOSFETs.

[0012] The vehicle charging circuit includes a first and a second terminal. The first terminal is connected to the first and third half-bridges, in particular to the connection point (phase potential) of the first and third half-bridges. The second terminal is connected to the second and third half-bridges, in particular to the connection point (phase potential) of these half-bridges.

[0013] The bridge circuit, the half-bridge, and in particular its semiconductor switches are line components and are designed, in particular, for lines exceeding 3 kW or 10 kW in both directions. The two connections can be designed according to a standard (or reference) for plugs designed for operating voltages exceeding 100 V, in particular according to the NEMA standard (wherein the first connection also takes into account the standard for charging sockets for electric vehicles). Furthermore, the first connection can be designed according to a standard for configuring charging plug connections or charging sockets for electric vehicles, with the adapter or additional contact set (also connected to the first and third half-bridges) being designed according to the NEMA standard.

[0014] The control mechanism is connected to the half-bridge control, in particular to the switch control of the half-bridge. The control mechanism is configured to control at least the first and second half-bridges in a pulse-wave-modulated manner, thereby generating a sinusoidal signal (averaged over time), for example, in the form of a positive half-wave and a negative half-wave of a sinusoidal voltage. The control mechanism controls the third half-bridge according to a rectangular signal, the two levels of which preferably correspond to the potential on the DC voltage side. A rectangular voltage is generated across the third half-bridge. Alternatively, the control mechanism is configured to control the third half-bridge according to a pulse-width-modulated rectangular signal, the two levels of which preferably lie between the potentials on the DC voltage side. The duty cycle of the two levels of the rectangular signal is preferably the same. This results in a rectangular voltage whose levels are symmetrical about the potential located midway between the two potentials of the DC voltage (on the DC voltage side). The duty cycle of the rectangular signal used to generate the rectangular voltage is, in particular, constant within a pulse of the rectangular voltage (corresponding to the duration of the half-wave).

[0015] The control mechanism is configured to convert the DC voltage on the DC voltage side of the bridge circuit into a sinusoidal signal, in particular, into successive positive and negative sinusoidal half-waves, through pulse wave modulation. A first and second half-bridge are used for this purpose. The successive sinusoidal half-waves have alternating polarity and are preferably offset relative to one another, in particular by the voltage amplitude used to control the third half-bridge (i.e., by the difference between the two levels of the square-wave voltage). The control mechanism is also configured to control the third half-bridge so that, in at least one mode, the third half-wave is controlled according to the square-wave signal used to generate the square-wave voltage. The edges of the square-wave voltage preferably coincide with the time at which the two half-waves of the first and second half-bridges succeed one another. In this context, only the curve form within a half-cycle is referred to as a half-wave and does not necessarily refer to the zero line. A half-wave can thus begin at the first potential of the DC voltage, the second potential of the DC voltage, the zero line, or any other voltage level.

[0016] The control mechanism is configured to control the first half-bridge to convert the DC voltage on the DC voltage side of the bridge circuit into a sinusoidal signal having a positive half-wave and a negative half-wave. Here, only the shape of the half-wave is described, not its voltage level. This sinusoidal voltage has a negative half-wave with a positive offset. A sinusoidal half-wave extending from the baseline in a negative direction is called a negative half-wave. The negative half-wave has a profile that corresponds to a sinusoidal profile within an angular range between 180° and 360°. The negative half-wave (i.e., the baseline) is positively offset, i.e., moves toward the positive potential of the DC voltage. In particular, the negative half-wave begins with the positive potential of the DC voltage. In particular, the negative half-wave begins with the positive edge of the square-wave voltage of the third half-bridge. The control mechanism is configured to control the first half-bridge to generate a negative half-wave with a positive offset and a first amplitude. Furthermore, the control mechanism is configured to control the second half-bridge to convert the DC voltage into a sinusoidal signal with a positive half-wave and a negative half-wave. Here, the negative half-wave is also positively offset. However, the negative half-wave generated by the second half-bridge has a second amplitude that is different from the first amplitude of the first half-bridge. The first and second half-bridges are thus controlled by the control mechanism to generate sinusoidal signals having positive and negative half-waves, respectively, but with different amplitudes of the sinusoidal voltage (first amplitude and second amplitude), and in particular with a positive offset of the negative half-wave of the pulsating sinusoidal voltage. In particular, the control mechanism is also configured to generate a positive half-wave of the pulsating sinusoidal voltage of the respective (first or second) half-bridge. The positive half-wave preferably originates from a negative potential of the DC voltage or also from a negative level of the square-wave voltage of the third half-bridge (whereas the negative half-waves of the first and second half-bridges originate from a positive level of the square-wave voltage of the third half-bridge).

[0017] The sinusoidal signal generated by the control mechanism and the first and second half-bridges alternately comprises positive and negative half-waves. The positive half-wave (excluding the position of the baseline) corresponds to a sinusoidal curve ranging from 0° to 180°. The negative half-wave (excluding the position of the baseline) corresponds to a sinusoidal curve ranging from 180° to 360°. The positive half-wave and the negative half-wave are offset relative to each other (in the amplitude direction). In particular, the positive half-wave is offset toward the negative potential of the DC voltage, while the negative half-wave is offset toward the positive potential. If the DC voltage applied to the half-bridge (on the DC voltage side) corresponds to a voltage between the potentials DC- (negative potential) and DC+ (positive potential), the positive half-wave is based on the potential DC- and is thus offset toward this potential. The negative half-wave is based on the potential DC+ and is thus offset toward this potential. The amplitude of the half-wave, or the amplitude of the pulsating sinusoidal voltage, is less than the level of the DC voltage (the difference between the potentials DC+ and DC-). The voltages generated by the first and second half-bridges, respectively, can be described as follows:

[0018] For x = 0° ... 180°: DC - + A sin(x) (= positive half-wave) and for x = 180° ... 360°: DC + - A sin(x) (= negative half-wave)

[0019] Where: A = half-wave amplitude,

[0020] x = the phase angle of the half-wave, and

[0021] DC+, DC-: The potential of the DC voltage on the DC voltage side of the bridge circuit

[0022] This applies to the sinusoidal voltages of the first and second half-bridges, the two half-bridges having different amplitudes A. The amplitude offset between the positive and negative half-waves corresponds to the difference between DC− and DC+.

[0023] Furthermore, the control mechanism is configured to control the third half-bridge to convert the DC voltage into a square-wave voltage having the potential of the DC voltage. This generates alternating square-wave voltage levels. The control mechanism is thus configured to control the bridge circuit to generate sinusoidal voltages with different amplitudes at each of the two connections. The sinusoidal voltage generated at the connections has continuous half-waves. In other words, the half-waves are not offset relative to one another (in terms of amplitude), but rather merge into one another at the transitions between the half-waves without substantially any (instantaneous amplitude) steps. This is achieved by the square-wave voltage of the third half-bridge, whose amplitude complements the offset of the two half-waves of different polarity generated by the first and second half-bridges.

[0024] Thus, a signal with two half-waves of different polarity, like a sinusoidal voltage, is referred to as a first and second sinusoidal signal, but in which the half-waves are offset relative to one another. In a sinusoidal signal, a potential step or voltage step occurs at each transition between successive half-waves of different polarity. A continuous voltage is referred to as a sinusoidal voltage, which may optionally have an (amplitude) offset relative to the potential difference, but in which successive half-waves of different polarity merge into one another essentially without a step. A sinusoidal signal is also a voltage signal, but is referred to by a different term to distinguish it from a sinusoidal voltage (which has "smooth," stepless transitions between half-waves).

[0025] The control device is designed to control the three half-bridges in such a way that two sinusoidal signals with different amplitudes are generated at two terminals (without a step-like transition between the half-bridges). This is achieved by combining the signal generated by the third half-bridge at the terminal with the signal of the first or second half-bridge, respectively, to form a sinusoidal voltage with a (step-free) amplitude. The two different amplitudes of the sinusoidal voltages at the two terminals enable simultaneous operation of loads with different rated voltages.

[0026] In particular, it is possible to connect a load with a first rated voltage to the first terminal and a load with a second rated voltage to the second terminal, thereby enabling both loads to be operated (either alternately or simultaneously) without having to change the load operating voltage or relocate the loads. The two terminals are connected to the half-bridges in such a way that, when the half-bridges are controlled as described herein, a sinusoidal voltage (without a step when switching between half-waves of different polarity) appears at each terminal. The two terminals are connected to a third half-bridge, which is controlled by a control mechanism to generate a rectangular voltage. Here, the two switches of the third half-bridge are alternately switched on and off, with the switch states remaining constant for the period of the rectangular circuit, and in particular, for the period of the sinusoidal half-wave. Furthermore, the first terminal is connected to the first half-bridge and the second terminal to the second half-bridge, so that, when these half-bridges are controlled in a pulse-width-modulated manner, different voltages can be generated with different amplitudes relative to the third half-bridge, even when the negative half-waves are shifted toward the positive potential. This results in sinusoidal voltages with different amplitudes. The first and second half-bridges each generate a sinusoidal signal with a first or second amplitude. The amplitude of this sinusoidal signal (the negative half-wave of which moves toward a positive potential and the positive half-wave of which moves toward a negative potential) refers to the maximum voltage difference within a half-wave (and not the maximum voltage difference across all half-waves). In other words, the term "amplitude" of a sinusoidal signal described here refers to the amplitude of a single half-wave and not the total amplitude, which would also include the voltage amplitude (voltage step) between the positive and negative half-waves.

[0027] The control device is preferably configured to actuate the bridge circuit to generate a first sinusoidal voltage at the first terminal and simultaneously to generate a second sinusoidal voltage at the second terminal. In this case, the first and second half-bridges are operated simultaneously to generate corresponding sinusoidal signals, thereby enabling two different sinusoidal voltages to be supplied simultaneously at the two terminals. In an alternative state, the control device can be configured to actuate either the first half-bridge or the second half-bridge to generate corresponding sinusoidal voltages, thereby enabling loads with different rated voltages to be connected to the two terminals, wherein these loads can be operated without switching between the terminals.

[0028] Preferably, the amplitude of the first voltage at the first terminal is approximately twice the amplitude of the second voltage at the second terminal. Thus, the first voltage is approximately twice the second voltage. In particular, the amplitude or voltage can be approximately doubled by being 1.8 to 2.2 times greater. The amplitude of the first voltage signal can also be approximately twice the amplitude of the second sinusoidal signal. In other words, the amplitude of the first sinusoidal signal can be 1.8 to 2.2 times the amplitude of the second sinusoidal signal. The negative and positive half-waves of the first voltage have the same amplitude. The positive and negative half-waves of the second sinusoidal signal also have the same amplitude.

[0029] The voltage amplitude of the first sinusoidal voltage half-wave preferably corresponds to 1.8 to 2.2 times the voltage amplitude of the second sinusoidal voltage half-wave. In other words, the amplitude of the first sinusoidal voltage half-wave is approximately twice the amplitude of the second sinusoidal voltage half-wave. The voltage amplitude of the rectangular voltage level is at least as great as the voltage amplitude of the first sinusoidal voltage half-wave (and also at least as great as the voltage amplitude of the second sinusoidal voltage half-wave). This also applies to the voltage amplitudes of the half-waves in the first and second sinusoidal signals. In particular, the voltage amplitude of the rectangular voltage (of the third half-bridge) corresponds to the DC voltage applied to the DC voltage side of the half-bridge.

[0030] The voltage amplitude of the square-wave voltage, that is, the voltage between its two levels, and the offset between the positive and negative half-waves in the first and second sinusoidal signals are designed such that the voltage amplitude of the square-wave voltage at the terminals produces a sinusoidal signal without (amplitude) steps between successive half-waves. The voltage offset between half-waves of different polarity in the first and second sinusoidal signals corresponds approximately to the voltage amplitude of the square-wave voltage, thereby enabling a substantially step-free transition between successive half-waves (of different polarity).

[0031] The negative half-wave of the first sinusoidal voltage has an offset that substantially corresponds to the positive offset of the negative half-wave of the second sinusoidal signal. In particular, at the transitions of successive half-waves in both sinusoidal signals, the half-waves are offset relative to each other by a potential difference that substantially corresponds to the voltage amplitude of the square-wave voltage. Depending on the reference potential, it can also be provided that the positive half-wave has an offset, i.e., a negative offset. In particular, the zero line of the positive half-wave of the sinusoidal signal corresponds to the negative potential of the DC voltage (or the negative level of the square-wave voltage), and the zero line of the negative half-wave of the sinusoidal signal corresponds to the positive potential of the DC voltage (or the negative level of the square-wave voltage). An offset occurs between the half-waves, which corresponds to the DC voltage level (or the difference between the levels of the square-wave voltage).

[0032] In one approach (assuming that the positive half-wave is not offset and is based on a negative voltage as the neutral line), the negative half-wave has a positive offset that corresponds to the DC voltage or voltage amplitude of the square wave voltage. In another approach based on the potential difference in the center between the two potentials of the neutral line or DC voltage, the positive half-wave has a negative offset that corresponds in magnitude to the positive offset of the negative half-wave. The sum of the magnitudes of the offsets of the positive half-wave and the offsets of the negative half-wave preferably corresponds to the potential difference of the DC voltage (in particular, to the level of the DC voltage) and in particular to the voltage amplitude of the square wave voltage generated by the third half-bridge.

[0033] The positive half-wave of the first sinusoidal signal and the positive half-wave of the second sinusoidal signal begin and end simultaneously. This also applies in particular to the negative half-wave. The half-waves of the sinusoidal signals are preferably synchronized with the edges of the rectangular voltage. The transitions between the half-waves in the sinusoidal signals preferably occur simultaneously with the edges of the rectangular voltage. The edges of the rectangular voltage correspond to transitions between different levels of the rectangular voltage, so that the transitions generated in the signal of the third half-bridge occur synchronously or simultaneously with the transitions between the half-waves in the sinusoidal signals of the first and second half-bridges.

[0034] The control mechanism is preferably configured to control the bridge circuit to generate a substantially sinusoidal voltage of 240V at the first terminal. The control mechanism is also configured to control the bridge circuit to generate a substantially sinusoidal voltage of 120V at the second terminal. In particular, the control mechanism is configured to control the bridge circuit to generate a sinusoidal voltage with a frequency of 60Hz. In particular, the control mechanism is configured to control the first and second half-bridges to generate half-waves with a frequency of 60Hz. In other words, the period duration of the half-waves generated by the first and second half-bridges corresponds to the period duration of a sine wave with a frequency of 60Hz. The suffix "substantially" preceding a numerical value means a deviation of no more than 20, 10, 5, or 2% from the stated value. In particular, the control mechanism is configured to generate an AC voltage at both terminals that complies with NFPA 70 (i.e., the North American standard for the low-voltage level of public power supply networks).

[0035] The described bidirectional vehicle charging circuit is specifically designed to generate a sinusoidal voltage at two terminals, starting from a DC voltage at the bridge voltage. Another function is, in particular, the (controlled) rectification of an AC voltage applied to at least one of the terminals to convert this AC voltage into a DC voltage. This allows the vehicle battery to be charged using an external AC power source. Therefore, in the charging state, the control device can be configured to control the bridge circuit to (controlled) rectify the AC voltage applied to the first terminal, thereby generating a DC voltage on the DC voltage side of the bridge circuit, in particular according to a target DC voltage. This charging state implements the aforementioned functions. The AC voltage applied to the first terminal can be a single-phase AC voltage or can be provided by multiple voltages of a single-phase three-wire power system, that is, a multi-phase voltage, where each phase corresponds to a voltage of the single-phase three-wire power system.

[0036] The vehicle charging circuit can include a separate inductor, via which the first phase potential, the second phase potential, and the neutral conductor potential are connected to a half-bridge (particularly the center point of the half-bridge) via its first and second terminals. The control mechanism can be configured to operate the bridge circuit with the separate inductor as a power factor correction (PFC) circuit in the charging state. The first half-bridge can be connected to the second phase potential via the first inductor. The second phase potential can also be referred to as the L2 potential and can be implemented as part of the first terminal, for example, as the second phase contact of the first terminal. The second half-bridge can be connected to the neutral conductor potential via the second inductor. The neutral conductor potential can be implemented as a neutral conductor contact in the respective terminal. The third half-bridge can be connected to the first phase potential via a third inductor. The first phase potential can be implemented as a part of the first and / or second terminal. Within the respective terminal, the first phase potential can be implemented as the first phase contact of the respective terminal. The terminals can also include a protective conductor contact or protective conductor potential.

[0037] The first connection can be designed as a NEMA socket for 240V AC. The second connection can be designed as a NEMA socket for 120V. In particular, the first connection can be designed according to one of the standards: NEMA (L) 5-15, -20, -30, -50 or NEMA 1-15. The second connection can be designed according to one of the standards: NEMA (L) 6-15, -20, -30, -50. The first and / or second connection can be designed according to one of the standards: NEMA (L) 14-20, -30, -50, or -60.

[0038] One embodiment provides that the vehicle charging circuit includes a changeover switch that connects the second half-bridge alternatively to the neutral conductor potential of the second connection or to the phase potential of the first connection. This phase potential of the first connection is, in particular, the phase potential connected to the first half-bridge (in particular, its connection point). If the changeover switch is in a first switching position, it connects the second half-bridge (or its connection point) to a second phase potential (L2) of the first connection. In a second switching position, the changeover switch connects the second half-bridge (i.e., its connection point) to the neutral conductor potential of the second connection. The second connection has a neutral conductor potential, wherein a neutral conductor potential may or may not be set at the first connection.

[0039] The vehicle charging circuit can include a disconnector that is arranged between the second connection and the third half-bridge. In particular, the disconnector is connected between an inductor connected to the third half-bridge and the first phase potential of the second connection.

[0040] The vehicle charging circuit may include an insulation monitor. The insulation monitor has inputs connected to the first phase potential, the second phase potential, and the neutral conductor potential of the terminals. In particular, the insulation monitor is connected to the first phase potential of the second terminal via a disconnector. In other words, the insulation monitor is not connected to the third half-bridge via a disconnector. The insulation monitor is preferably connected to the half-bridge via an inductor. The insulation monitor can be connected to the neutral conductor, with the resulting connection point connected to the second half-bridge via a changeover switch. If both terminals have neutral conductor potential, the two terminals can be connected to each other. The second terminal is preferably a socket inside the vehicle. The second terminal can be designed as a charging socket for charging the electric vehicle using an external charging voltage source. The first terminal can include an adapter for outputting AC voltage, which is designed according to one of the aforementioned NEMA standards for 240V AC. Thus, the first terminal can be a two-part component and can include both the charging socket and the adapter, which can be plugged into the charging socket and also allows the connection of standard 240V loads.

[0041] The vehicle charging circuit can include a DC voltage converter. This DC voltage converter is connected downstream of the DC voltage side of the bridge circuit. The vehicle charging circuit can include a battery-to-vehicle electrical system tapping connection. This battery-to-vehicle electrical system tapping connection is connected to the DC voltage side of the bridge circuit via a DC voltage converter. The vehicle's high-voltage traction battery can be connected to the battery-to-vehicle electrical system tapping connection.

[0042] Furthermore, a vehicle electrical system is described that has a bidirectional vehicle charging circuit as described above. Furthermore, the vehicle electrical system includes a high-voltage battery, in particular a traction high-voltage battery. This high-voltage battery is connected to a battery-to-vehicle electrical system tapping connection of the vehicle charging circuit. The battery-to-vehicle electrical system tapping connection can be connected directly or indirectly to the DC side of the bridge circuit. The battery-to-vehicle electrical system tapping connection can be connected to the high-voltage battery directly (without a converter) or via a (electrically separate or non-separate) DC voltage converter. Instead of a high-voltage battery, the vehicle electrical system can also generally include an onboard electrical system tapping connection that includes a high-voltage storage device and is connected to the battery-to-vehicle electrical system tapping connection as described herein.

[0043] The circuit described here allows the provision of an AC voltage similar to that commonly used in North American power grids. Two different voltage levels are provided at at least two different connections by means of a single circuit. This allows different loads to be supplied with different rated voltages simultaneously or without disconnecting them. This applies in particular to 120V and 240V loads. One of the connections can be configured as a charging connection, wherein a common socket or common socket contacts for 240V are provided by an adapter that can be plugged into the charging socket. The adapter thus has two ends, one of which is designed to be plugged into the charging socket of an electric vehicle and the other end forms a socket, in particular for 240V loads. Instead of the adapter, a socket can also be provided, which is connected in parallel with the charging socket, wherein this parallel circuit is then connected to the bridge circuit as the second connection.

[0044] The circuit shown here is particularly a vehicle-side charger (On-Board Charge, OBC), with which a power factor correction filter can be constructed. For this purpose, in addition to the half-bridge, inductors can also be provided, which together with the half-bridge represent a controlled rectifier that also serves as a power factor correction filter. During operation in the reverse direction, the DC voltage on the DC voltage side is converted into two different AC voltages (sinusoidal voltages) using a bridge circuit, as described above. A single-pole changeover switch (EIN-EIN) (SPDT) can be provided between one half-bridge, particularly the second half-bridge, and the connection. The connection on the half-bridge side can be selectively connected to the first connection or the second connection. In particular, the changeover switch selectively connects the second half-bridge to phase L2 of the first connection or to the neutral conductor potential or neutral conductor contact of the second connection. When the second half-bridge is selectively connected to the first connection (phase L2), the second half-bridge is connected in parallel with the first half-bridge, thereby generating a higher current at the first connection. A first voltage is then generated at the first terminal, but the first and second half-bridges contribute to converting this voltage, thereby enabling higher currents. If the changeover switch connects the second half-bridge to the second terminal (neutral conductor potential), different sinusoidal voltages can be generated simultaneously at both terminals. The second half-bridge is then used to generate the second voltage at the second terminal, and the first half-bridge is used to generate the first (higher) sinusoidal voltage at the first terminal.

[0045] The disconnector described here between the third half-bridge and the second connection (particularly its L1 phase potential) can be designed for a maximum voltage that is lower than the first voltage, that is, that corresponds to the second voltage. Both the first connection and the second connection can have an L1 phase (particularly as contacts), with these phases being connected to one another. The connection between these phases is preferably made on the side of the disconnector connected to the third half-bridge. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 For a more detailed explanation of the specific embodiments of the bidirectional vehicle charging circuit described here and the onboard electrical system described here.

[0047] Figure 2 The voltages of three half-bridges are shown by way of example and serve to explain the control of the bridge circuit. DETAILED DESCRIPTION

[0048] Figure 1The diagram shows a charging circuit LS inside an electric vehicle, which is connected to a vehicle-internal interface EV to enable connection to external devices EX. The charging circuit LS has a first connection A1', which is connected to a connection device A1, to which a load 1 is connected, in turn, as an example. The charging circuit also has a second connection A2', which is connected to a vehicle-internal connection device A2. Because the connections are directly connected to the corresponding connection devices and thus generate the same electrical potential, no distinction is made between the connection devices and the connections to simplify the description of the electrical connections. In an electromechanical implementation, the connections A1' and A2', as components of the power circuit, can be designed as (internal) connecting elements or screwed connections, or they can be formed by a continuous conductor extending from the interior of the vehicle circuit LS to the connections A1 and A2. As described, the first connection A1 can be a two-part component, comprising a vehicle charging socket as (part of) the vehicle-side interface and an adapter that plugs into it. The adapter has one end and a second end connected thereto, wherein the first end is designed to be plugged into a charging socket of a vehicle, and the second end forms a socket for a load (especially for a 240V load). The socket is preferably designed according to one of the NEMA (L) 6-15, -20, -30, -50 standards or according to the NEMA (L) 14-20, -30, -50, or -60 standards.

[0049] The bidirectional vehicle charging circuit has a bridge circuit with three half-bridges B1, B2, and B3. Each half-bridge has two transistors connected in series, which are connected to each other via connections U1, U2, and U3, and whose ends are connected to the DC voltage potentials DC+ and DC- on the DC voltage side of the bridge circuit. The connection points between the transistors of each half-bridge have potentials, which are designated by the same reference numerals U1 to U3 for better clarity. The DC voltage side of the bridge circuit (and thus the DC voltage potentials DC+ and DC-) is connected to the onboard power supply tap connections B+ and B- via an optional, electrically (separate) DC voltage converter W. The onboard power supply tap connections B+ and B- are part of the charging circuit and are designed to connect to internal vehicle circuits, such as the high-power battery or the battery-to-onboard power supply tap connection. Connections B+ and B- are also referred to as battery-to-onboard power supply tap connections. An intermediate circuit capacitor C, which here by way of example comprises two capacitors connected in series, is likewise connected to the DC voltage side of the bridge circuit (half-bridges B1 to B3 ).

[0050] The potentials or connection points U1, U2, and U3 of half-bridges B1 to B3 form the AC voltage side of the bridge circuit. This AC voltage side is connected to terminals A1, A2, or A1', A2', via three (separate) inductors I1 to I3. One of the inductors I1 to I3 is connected between each of the connection points U1 to U3 (i.e., each of the AC voltage potentials of the AC voltage side of the bridge circuit) and terminals A1, A2, or A1', A2'. Together with the bridge circuits B1 to B3, the inductors I1 to I3 form a power factor correction filter (PFC).

[0051] Furthermore, the functional principle with the closed isolating switch TS and the changeover switch US in the switch position 2 is observed, as shown. An operating mode is observed in which the bridge circuits B1 to B3 are controlled by a control device C in order to convert the voltage on the DC voltage side (DC+, DC-) into an AC voltage at the first and second terminals A1, A1', A2, A2'. The control device C controls the switches or transistors of the bridge circuits B1 to B3 as follows: the first half-bridge is controlled in order to convert the DC voltage DC on the DC voltage side of the bridge circuit into a first sinusoidal signal with a negative half-wave having a positive offset. The half-wave of the sinusoidal signal has a first amplitude. This first amplitude is represented by NH1 at Figure 2 . The first sinusoidal signal has a positive half-wave, which relates to the negative potential DC of the direct voltage. One way of observing this is that the positive half-wave is also offset, that is, negatively offset. Instead of observing the individual offsets of the individual half-waves, it is also possible to illustrate the curve shape by a sinusoidal signal having a positive half-wave PHW and a negative half-wave NHW that are offset relative to each other. In particular, these half-waves are offset relative to each other by the rectangular voltage U3 generated by the third half-bridge. The second sinusoidal signal U2 is generated in the same way as the first sinusoidal signal and has the same signal characteristics as the first sinusoidal signal except for the amplitude. According to Figure 2 It can be seen that the second sinusoidal signal has a positively offset negative half-wave H2. According to another way of looking at it, the positive half-wave and the negative half-wave of the second sinusoidal signal are offset relative to each other. As in the first sinusoidal signal, the negative half-wave in the second sinusoidal signal is also positively offset relative to the positive half-wave. The offset between the half-waves of different polarity in the second sinusoidal signal corresponds to the offset between the half-waves of different polarity in the first sinusoidal signal. The offset between the half-waves of different polarity in the first sinusoidal signal corresponds to the amplitude of the rectangular voltage U3. This also applies to the second sinusoidal signal U2. The amplitude or offset between the levels in the rectangular voltage H3 is greater than the amplitudes H1, H2 of the half-waves of the sinusoidal signal. The amplitude of the rectangular voltage Figure 2 The amplitude or magnitude shown in (voltage difference between two levels within the square-wave voltage) corresponds to the direct voltage DC, ie the difference between the potentials DC+, DC−.

[0052] In addition, Figure 2, the voltage U2 has an amplitude which corresponds approximately to twice the amplitude of the voltage U2. In particular, the voltage U1 has an amplitude of a sinusoidal wave which corresponds to an effective AC voltage of 240 V. The voltage U2 has an amplitude of an AC voltage which corresponds to the effective value of an AC current of 120 V. The sinusoidal voltage V1 at the first connection is between the phases L1 and L2 of the first connection. The voltage is generated by a combination of the potentials U1 and U3 or between the phase potentials P1 and P3 on the sides of the inductors I1 and I3 which face the connections A1, A2. About Figure 2 , which means that voltage V1 corresponds to the potential difference U1, U3. For the positive half-wave, this means a positive half-wave with amplitude H1, and for the negative half-wave, this means amplitude H1 (negative half-wave), with the two half-waves joining without steps. The stepless transitions are produced by the fact that the half-waves PHW, NHW of the first sinusoidal signal U1 shift or jump during the transitions between half-waves in the same manner as the potential of the square-wave voltage. The second sinusoidal voltage V2 is produced by the potential difference between the signals U2, U3 of the second and third half-bridges B2, B3. Here, during the transitions between half-waves, the second sinusoidal signal also jumps, just as the level in the square-wave voltage changes synchronously. This also results in a (continuous) sine wave or sinusoidal voltage V2 that is essentially stepless. As a result, the shifts between half-waves, or the shifts of the negative half-waves in the sinusoidal signal, are canceled out by the square-wave voltage.

[0053] In the charging state, an AC voltage can be applied, in particular, to the first terminal A1 or A1'. This AC voltage is rectified in a controlled manner by the three half-bridges B1-B3 and, in particular, the inductors I1 to I3, to thereby generate a DC voltage. This DC voltage can be transmitted directly or via an optional converter W to the terminals B+, B- to thereby charge a battery that can be connected thereto. This operation corresponds to the conventional leveling operation generated by a power factor correction filter PFC.

[0054] When converting or commutating a DC voltage into AC voltages V1 and V2, two different states exist. In the first state, the changeover switch connects the second half-bridge B2 or the inductor I2 connected thereto (and thus the phase connection P2 of the bridge circuit) to the second phase L2 of the first connection A1. In this state, B1 and B2 operate synchronously and in the same manner, thus jointly carrying twice the current and thereby generating a voltage V1 that can be output with high current. In this state, the disconnector TS can be opened, in particular to prevent interfering voltages from being applied to the second connection. In the other state, the changeover switch US is in switch position 2. In this case, the first half-bridge is connected to the second phase connection L2, the first phase L1 of the first and second connections is connected to the third half-bridge, and the neutral conductor potential N of the connections A1 and A2 (or A1' and A2') is connected to the second half-bridge. Connection to the half-bridges is via their AC voltage sides, i.e., via connection points U1 to U3. In this case, the first half-bridge is actuated to generate a first sinusoidal signal, and the second half-bridge is actuated to generate a second sinusoidal signal, whose half-wave has a smaller amplitude than the half-wave of the first sinusoidal voltage. Two different sinusoidal voltages are then generated at terminals A1 and A2 (without a step at the half-wave transition). This allows for simultaneous power supply to loads 1 and 2 with different rated voltages. In particular, a voltage of 240V effective AC voltage can then be generated at terminal A1 to supply load 1, which is rated at this voltage. A voltage of 120V effective AC voltage can be generated at terminal A2 to supply load 2, which has this voltage as its rated voltage. In this state, disconnector TS is closed to allow the voltage to be output at terminals A2 or A2'.

[0055] The insulation monitor IM has inputs connected to phases L1 and L2, as well as to the neutral conductor potential N and the protective conductor potential M. If the optional disconnector TS is present, the insulation monitor IM is preferably connected to the side of the disconnector that is also connected to the third half-bridge or bridge switch or the upstream inductors I1 to I3. The input connected to phase L2 is preferably connected to the side of the changeover switch US facing the first connection A1. The insulation monitor IM can be controllably connected to a control unit C in order to permanently disconnect all switches of the half-bridges B1 to B3 if an insulation fault is detected. The control unit C is preferably controllably connected to the changeover switch US and / or the disconnector TS.

[0056] Figure 2As mentioned, two sinusoidal signals are shown as examples. These differ from pure sine waves in that the successive half-waves of different polarity are offset relative to one another (in amplitude). The positive half-wave PHW is offset negatively relative to the negative half-wave NHW. This offset corresponds to the amplitude or magnitude of square-wave voltage U3. Voltages U1 to U3 are plotted relative to the potential DC- and correspond to the potential at the connection points of the three half-bridges B1 to B3. Only square-wave voltage U3, shown, has two voltage levels that alternate between DC+ and DC-. Sinusoidal signals U1 and U2 have smaller amplitudes (H1 and H2). Square-wave voltage U3 is generated by alternating opening and closing of the switches of half-bridge B3. The switch states remain constant within a half-wave (period). In contrast, sinusoidal half-waves are generated by pulse-wave modulation (via a control unit C) in each of the first and second half-bridges B1 and B2. The resulting envelope of the signals generated by pulse-width modulation in half-bridges B1 and B2 has the same period as the square-wave voltage. In other words, the sinusoidal signal is synchronized with the sine wave of the square-wave voltage and is of the same length. Preferably, the sinusoidal signal and the square-wave voltage have a frequency of 60 Hz (or 50 Hz).

Claims

1. A bidirectional vehicle charging circuit (LS) having a multi-phase bridge circuit, the bridge circuit having a first, a second and a third half-bridge (B1-B3), wherein a first terminal (A1') is connected to at least the first and the third half-bridge (B1, B3), and a second terminal (A2') is connected to at least the second and the third half-bridge (B2, B3), wherein a control device (C) is connected to the first, the second and the third half-bridge and is configured to: actuate the first half-bridge (B1) in order to convert a DC voltage (DC) on the DC voltage side of the bridge circuit into a DC voltage with a positive offset and a first amplitude; A first sinusoidal signal of a negative half-wave (NH1); controlling the second half-bridge (B2) to convert the direct voltage (DC) into a second sinusoidal signal of a negative half-wave (NH2) with a positive offset and a second amplitude; and controlling the third half-bridge to convert the direct voltage (DC) into a rectangular voltage having the potential (DC+, DC-) of the direct voltage (DC) as alternating rectangular voltage levels, wherein the control device (C) is configured to control the bridge circuit so as to generate sinusoidal voltages (V1, V2) with different amplitudes at the two terminals (A1', A2').

2. The bidirectional vehicle charging circuit (LS) according to claim 1 , wherein the control device (C) is configured to actuate the bridge circuit in order to generate a first sinusoidal voltage at the first terminal ( A1 ′) and simultaneously to generate a second sinusoidal voltage at the second terminal ( A2 ′).

3. The bidirectional vehicle charging circuit (LS) according to claim 1 or 2, wherein the amplitude of the first voltage (V1) at the first terminal (A1') applied to the two phase potentials (L1, L2) of the first terminal (A1') is 1.8 to 2.2 times the amplitude of the second voltage (V2) at the second terminal (A2') applied between the phase potential (L1) of the second terminal (A2') and the neutral conductor potential (N).

4. The bidirectional vehicle charging circuit (LS) according to claim 1 , 2 or 3 , wherein the voltage amplitude (h1) of a half-cycle of the first sinusoidal voltage (U1) corresponds to 1.8 to 2.2 times the voltage amplitude (h2) of a half-cycle of the second sinusoidal voltage (U2), and the voltage amplitude (h3) of the square-wave voltage (U3) corresponds to or is greater than the voltage amplitude (h1) of a half-cycle of the first sinusoidal voltage (U1).

5. A bidirectional vehicle charging circuit (LS) according to any one of claims 1 to 4, wherein the negative half-waves of the first and second sinusoidal signals have the same positive offset, wherein this offset corresponds to the potential difference between the rectangular voltage levels (DC+, DC-) of the rectangular voltage.

6. A bidirectional vehicle charging circuit (LS) according to any one of claims 1 to 5, wherein the positively offset negative half-waves of the first and second sinusoidal signals start and end simultaneously at the instants of occurrence of the flanks of the rectangular voltage.

7. The bidirectional vehicle charging circuit (LS) according to claim 1 , wherein the control device (C) is configured to actuate the bridge circuit in order to generate a sinusoidal voltage (V1) of substantially 240 V at the first terminal and a sinusoidal voltage (V2) of substantially 120 V at the second terminal, wherein the sinusoidal voltage has a frequency of substantially 60 Hz.

8. A bidirectional vehicle charging circuit (LS) according to claim 1 , wherein the control device (C) is configured to actuate the bridge circuit in the charging state in order to rectify an AC voltage present at the first terminal into a DC voltage (DC) on the DC voltage side of the bridge circuit (B1-B3).

9. A bidirectional vehicle charging circuit (LS) according to claim 1 , wherein the half-bridge (B1-B3) is connected to the first phase potential (L1), the second phase potential (L2) and the neutral conductor potential (N) of the first and second connections (A1, A2) via separate inductors (I1-I3), wherein the control device (C) is designed to operate the bridge circuit together with the separate inductors (I1-I3) as a power factor correction circuit (PFC) in the charging state.

10. The bidirectional vehicle charging circuit (LS) according to claim 1 , comprising a changeover switch (US) which connects the second half-bridge (B2) alternatively to the neutral conductor potential (N) of the second connection (A2) or to the phase potential (L2) of the first connection (A1), the phase potential of which is connected to the first half-bridge (B1).

11. The bidirectional vehicle charging circuit (LS) according to claim 1, further comprising a disconnect switch (TS) which is arranged between the second connection and the third half-bridge (B3).

12. The bidirectional vehicle charging circuit (LS) according to claim 1, further comprising an insulation monitor (IM) which is connected to the phase potentials (L1, L2) of the first and second connections and to the neutral conductor potential (N).

13. The bidirectional vehicle charging circuit (LS) according to claim 1 , wherein a DC voltage converter (W) is connected downstream of the DC voltage side of the bridge circuit, said DC voltage converter connecting the bridge circuit to the battery-onboard power supply branch connections (B+, B−) of the vehicle charging circuit (LS).

14. A vehicle electrical system having a bidirectional vehicle charging circuit (LS) according to claim 1, wherein the vehicle electrical system further comprises a high-voltage battery, which is connected directly or via a DC converter (W) to the battery-to-vehicle electrical system branch connections (B+, B-) of the vehicle charging circuit (LS).

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