Patent Application
20220029442
The present invention relates to an assembly for switching a high-voltage battery in a vehicle, a system having a high-voltage battery, a circuit assembly and a consumer circuit, and a vehicle which has such an assembly and such a system. In addition, the invention relates to a method for connecting and a method for disconnecting a battery.
The term “switching a battery”, i.e. switching a battery on or off, is used here to mean the connection or disconnection of the battery to or from a consumer circuit. Similarly, connection and disconnection of the battery are intended to mean connection to and disconnection from a consumer circuit. A consumer circuit has, for example, an electric motor, control circuits, voltage transformers and further consumers in the vehicle and typically has capacitances and inductances.
High-voltage batteries in vehicles are generally mechanically or electromechanically disconnected or connected to the consumer circuit via switches. The switches are arranged both at the positive terminal and at the negative terminal of the battery. Typically, relays are used as switches. Since a connection by means of a relay is produced without any directional sense, the circuit is provided with two paths, each having a switch, at the positive terminal. In this case, one path is used for precharging the capacitances of the downstream circuit, while the other is provided for the time period after the precharging. Therefore, in total three relays are required: one for the precharging path and one for the switch-on path at the positive terminal and one at the negative terminal. The connections are in this case bidirectional, i.e. the current can flow in each path, both towards the battery or away from the battery and towards the consumer circuit.
The precharging circuit is used for limiting the switch-on current which is produced, for example, in the case of high-capacitance consumers when a high voltage is applied. For this purpose, a resistor is used, for example, which is arranged in the precharging path. As soon as the capacitances are charged, there is a switchover to the other path without the resistor, with the result that no losses and no heat occur at the resistor as time goes on.
The driving of three relays is complex. In addition, relays are susceptible to wear, and the precharging current cannot be regulated.
It is therefore the object of the present invention to provide a cost-effective and efficient circuit assembly for switching a high-voltage battery.
The object is achieved by a circuit assembly, a system, a motor vehicle and methods as claimed in the independent claims. The respectively back-referenced dependent claims reflect advantageous developments of the invention.
In accordance with one aspect, a circuit assembly for switching a high-voltage battery is provided. The circuit assembly has a precharging circuit, which is designed for connection to a first terminal of the high-voltage battery and for precharging a consumer, having a transistor for conducting a current from the battery to the consumer and a diode arranged back-to-back in parallel with the transistor for conducting a return current into the battery.
With this assembly, electronic switching is enabled, with the result that energy is transported from the battery to a consumer via the drain-source path of the transistor. Both the switching-on and the switching-off are implemented without any mechanical components. Furthermore, the diode enables a return flow of energy from the consumer circuit, i.e. from the circuit connected to the circuit assembly, into the battery. Such a return flow can originate, for example, from a further battery in the connected circuit, from inductions in the consumer circuit or from a charging operation.
In accordance with one exemplary embodiment, the transistor is a silicon carbide MOSFET (metal-oxide-semiconductor field-effect transistor) semiconductor (SiC MOSFET), and the diode is integrated in the silicon carbide MOSFET semiconductor. SiC MOSFETs have a relatively high degree of robustness and are additionally well suited to high switching frequencies. Furthermore, a SiC MOSFET has considerably lower power losses. Reduced power losses result in a higher efficiency and in lower system costs and sizes owing to the decreased amount of cooling complexity involved.
In accordance with one exemplary embodiment, the transistor is configured to switch in pulsed fashion during switching-on of the consumer during a precharging phase.
In this case, the precharging phase can in particular be a phase in which the capacitances of the consumer circuit are charged and can last until said capacitances are sufficiently charged. Sufficiently in this case means that no impermissibly high currents flow when the transistor is permanently switched on, which corresponds to a second phase. In this case, a safety margin can be taken into consideration.
Owing to the pulses, the capacitances are charged gradually in a defined manner, and therefore a low and monitored current is output to the consumer circuit virtually without losses for precharging. As a result, a resistor for precharging becomes superfluous. The driving of a second switch, such as, for example, a relay or switchover between two switches can be dispensed with. Therefore, the circuit assembly can replace, for example, two paths, i.e. both the direct connection and the precharging path at the positive terminal of the battery, and additionally enables an energy flow to the battery. If a SiC MOSFET with an integrated inverse diode is used, only one component is necessary for this. Furthermore, the good switchability of SiC MOSFETs in particular in the pulsed operating mode for precharging is advantageous.
In accordance with one exemplary embodiment, the circuit assembly has a switch, which is designed for connection to a second terminal of the high-voltage battery. The switch is implemented, for example, by a relay. As a result, the return current flow can be prevented, if necessary.
In accordance with one aspect, a system for switching a high-voltage battery is provided. The system has a circuit assembly as described above, a high-voltage battery, and a consumer circuit, wherein the first terminal of the high-voltage battery is connectable to the precharging circuit, and wherein the precharging circuit is connectable to a positive line of the consumer circuit. The consumer circuit has capacitive properties.
This aspect therefore includes the circuit assembly with the battery on one circuit assembly side and the consumer circuit on the other circuit assembly side, wherein the circuit assembly represents the connecting element between the battery and the consumer circuit. In particular, the circuit assembly is connected to the positive terminal of the battery on one side and the positive supply line of the consumer circuit. The circuit assembly in particular takes account of the capacitive properties of the consumer circuit by virtue of the precharging circuit.
In accordance with one embodiment, the second terminal of the high-voltage battery in the system is connectable to a relay, and the relay is connectable to a negative line of the consumer circuit. The second terminal can in particular be the negative terminal of the battery, which can be connected, via the relay, to the negative line of the consumer circuit. By virtue of this relay, the circuit via the battery, i.e. the current flow from or to the battery, can be disconnected.
In accordance with one aspect, in a method for connecting a high-voltage battery in a vehicle with an assembly as described above, in a first phase, during the connection the transistor is switched in pulsed fashion, and, in a second phase, during the connection the transistor is switched on. In this case, “switched on” is understood to mean that the transistor is switched so as to be conducting. By virtue of the pulsed switching, in the first phase the precharging is enabled. In the second phase, the battery is connected to the consumer circuit via the conducting transistor.
In accordance with one embodiment, the first phase is concluded when the consumer is approximately or completely charged. The purpose of the first phase, in which the current flows in pulsed fashion via the transistors, is that the battery and the electronic component parts, including the lines, are not overloaded by the current flow to the capacitances. Secondly, the current flow during charging of a capacitance asymptotically approaches zero. Therefore, the capacitive consumer should be charged in pulsed fashion until it is ensured that no overloads occur, wherein this is not necessarily at 100% charge.
In accordance with one aspect, in a method for disconnecting a high-voltage battery in a vehicle having an assembly as described above, the transistor is turned off, and a return current is conducted via the diode to the battery.
In accordance with one aspect of the invention, a vehicle is provided, which has a circuit assembly as described above. In this case, a vehicle can be, for example, an electric vehicle, a vehicle with a hybrid drive, a heavy goods vehicle or a bus. Furthermore, the vehicles can be operated with overhead lines or on rails. Within the further meaning, vehicles are also understood to mean electrically driven boats or aircraft or airplanes.
Exemplary embodiments of the invention are illustrated in the drawings and will be explained in more detail in the description below. In the drawings:
In general, the switch 205 can be closed, but it can be opened for completely disconnecting the battery 201, if necessary. If the battery 201 is connected, a pulsed signal is applied to the gate of the transistor 203, with the result that the capacitances of the consumer circuit are precharged with short current bursts. The effective current intensity can be controlled by the pulse widths until the capacitances are charged. It is therefore possible, for example, to regulate the current intensity at the start by short pulses, and to extend the pulses gradually until there is a steady signal, with the result that, after the precharging phase, the transistor is permanently switched on, i.e. when there is no longer a precharging current flowing or only a low precharging current flows. Alternatively, the current could also be controlled via an analog gate voltage. In this case, a drive circuit for the gate voltage is required, which initially severely limits the battery current during switching-on and then gradually reduces the limitation.
In order to disconnect the high-voltage battery 201, the transistor 203 is turned off via the gate voltage. The return current can now flow via the integrated diode 202 towards the battery 201. The battery 201 can additionally be mechanically disconnected via the switch 205. This can be used, for example, when it is desirable for there to be no return current flow into the battery.
The system for switching a high-voltage battery, in one embodiment, has a circuit assembly having at least one precharging circuit 204, a high-voltage battery 201 and a consumer circuit 206 having capacitive properties. The circuit assembly can furthermore have the switch 205.
The high-voltage battery 201 can be located at a suitable position in the vehicle, such as, for example, in the vicinity of the front axle or the rear axle. The circuit assembly is preferably located in the vicinity of the battery, with the result that the potential-carrying lines at the terminals of the battery are short. In general, the circuit can also be arranged so as to be physically remote from the battery.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2018 221 426.3 | Dec 2018 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/083958 | 12/6/2019 | WO | 00 |
