Driving circuit, battery management system, and driving method

Abstract

The present disclosure relates to a driving circuit for driving coils (21, 22, 23) of a plurality of electromagnetic switching devices, a battery management system comprising the driving circuit and a driving method. The driving circuit (100, 200, 300) comprises a power supply side circuit, which comprises a power supply side switch (108, 308) for controlling power supply of the coils (21, 22, 23) of the plurality of electromagnetic switching devices, a ground side circuit, which comprises a plurality of ground side switches (110, 310), wherein each of the plurality of ground side switches (110, 310) is adapted to electrically connect one of the coils (21, 22, 23) of the plurality of electromagnetic switching devices to a ground potential, and a control circuit for controlling the switching of the power supply side switch (108, 308) and the switching of the plurality of ground side switches (110, 310) to individually supply the coils (21, 22, 23) of the plurality of electromagnetic switching devices at least with a pick-up current for switching the respective one of the plurality of electromagnetic switching devices from an open state into a close state, or a hold-on current for holding the respective one of the plurality of electromagnetic switching devices in the close state.

Description

[0001] Driving circuit, battery management system, and driving method

[0002] The present disclosure relates to a driving circuit for driving coils of a plurality of contactor devices, a battery management system comprising the driving circuit and a driving method.

[0003] With the advanced development of electric vehicles (EV), in particular battery electric vehicles (BEV), and hybrid electric vehicles (HEV), in particular plug-in hybrid electric vehicles (PHEV), high voltage batteries become more and more common in vehicles like buses, trucks or passenger cars.

[0004] Typically, electric vehicles use driving batteries with high voltages, for example with voltages equal to 400 V or to 800 V DC or even higher voltages, in order to power an electric motor, which drives the electric vehicle. Stationary battery systems are oftentimes built which even higher voltages, for example equal to or above 1500 V DC. It is a common safety feature that the high voltage battery can be disconnected from other circuits of the high voltage system by opening one or more electromagnetic switch device, such as a contactor or other electromagnetically actuated switch devices. In electric vehicles, battery packs oftentimes contain a positive and a negative contactor, which are respectively electrically connected in series to one of the two poles of the high voltage battery. In addition there are also contactors which switch both the positive and the negative battery pole with one electromagnet as for example described in European patent application EP 3 933 878 A1 . In many electric vehicle applications, more than two contactors or other electromagnetic switching devices are provided, in order to switch on and off additional circuits, which are also supplied by the driving battery. These additional circuits can be, for example, a DC charging circuit, one or more motor controller circuits, or auxiliary load circuits for a DCDC converter, high voltage AC compressors, or other devices.

[0005] Typically, contactors used in high voltage applications have a low voltage coil, for example supplied by the low voltage auxiliary battery of the electric vehicle, which needs to be energized in order to create a magnetic field, which in turn actuates the contactor. Hereby, the pick-up current of a contactor, which needs to be supplied to the coil when closing the contactor, is typically higher than the hold current, which needs to be supplied to the coil to keep the contactor closed. Therefore, to enhance energy efficiency of the battery system by reducing losses in the contactor coils, it is known to implement a circuit which can provide higher power during the contactor pick-up phase and a separate circuit, which can supply a lower power during to the contactor hold phase as it is for example described in European patent application EP 2 513 938 A1. Another possibility to reduce the losses in the contactor coils is to drive the contactor coil by using a PWM circuit as for example described in European patent application EP 3 432 334 A1. Oftentimes, in these implementations, the high pick-up current is achieved by connecting a fixed voltage, e.g. the low voltage supply voltage of an auxiliary battery in an electric vehicle directly to the contactor coil for a defined time interval (e.g. 150 ms) and then apply a PWM signal to a power supply side switch, which is provided between the voltage source and the contactor coil, in order to reduce the coil current. The PWM circuit is controlled to provide a suitable switching frequency for the power supply side switch, so that due the coil inductance a DC current is obtained instead of a square wave current. However, PWM circuits in contactor coil drive circuits are problematic in terms of electromagnetic interference and radio emissions. Close care must be taken in the circuit design and the overall battery system or HV system design, which makes an appropriate circuit design complicated and cumbersome.

[0006] Moreover, for reasons of functional safety, it is desirable to have more than one switch (e.g. a semiconductor switch like a transistor) electrically connected in series to each contactor coil for controlling power supply of the contactor coil. This way, it is guaranteed that the contactor can always be safely disconnected, even in case of a single point fault that causes one of the two switches to be stuck closed. Fig. 6 shows a simplified circuit diagram, where a contactor coil 10 (inductance) is electrically connected by a power supply side switch (or “hi-side switch”) 12, like a p-type metal-oxide semiconductor (PMOS) switch as an example of a transistor, to the high potential of a supply battery, and by a ground side switch (or “lo-side switch”) 14, like a n-type metal- oxide semiconductor (NMOS) switch as an example of a transistor, to a ground potential, which is defined by the low potential of the supply battery.

[0007] In this context, the inventors of the present invention have found, that in cases where a plurality of contactor devices need to be controlled in an HV power supply system, the design of appropriate contactor coil driving circuits becomes complicated and has a large impact on the system space and costs, since multiple instances of control circuits need to be provided. Especially, it is a disadvantage that the common designs require to provide both of the supply circuits to differentiate between providing pick-up current and providing hold current to the coil and to provide the grounding circuit that provides a redundant shut-down path for functional safety for all of the implemented contactor devices. This has the result that in the common designs the required circuits typically feature several PWM circuits, each containing the two switches and the PWM feature.

[0008] Accordingly, it is an object of the present invention to provide a driving circuit for driving coils of a plurality of contactor devices, a battery management system comprising the driving circuit, and a driving method, which can overcome the above described disadvantages and simplifies the circuit design. Furthermore, it is an object of the present invention to provide a compact and economic solution.

[0009] At least one of these objects is solved by the present invention as defined in the independent claims.

[0010] In particular, according to a first aspect of the present disclosure, there is provided a driving circuit for driving coils of a plurality of electromagnetic switching devices. The driving circuit comprises a power supply side circuit, which comprises a power supply side switch for controlling power supply of the coils of the plurality of electromagnetic switching devices, a ground side circuit, which comprises a plurality of ground side switches, wherein each of the plurality of ground side switches is adapted to electrically connect one of the coils of the plurality of electromagnetic switching devices to a ground potential, and a control circuit for controlling the switching of the power supply side switch and the switching of the plurality of ground side switches to individually supply the coils of the plurality of electromagnetic switching devices at least with a pick-up current for switching the respective one of the plurality of electromagnetic switching devices from an open state into a close state, or a hold-on current for holding the respective one of the plurality of electromagnetic switching devices in the close state.

[0011] By providing a common power supply side switch for all coils (e.g. contactor coils) electrically connected to the driving circuit, it is possible to unify the power supply for all connected coils. At the same time, it is possible to individually control the current flow through each of the connected coils individually by connecting one of the plurality of ground side switches to each coil. Consequently, the connected coils can be safely disconnected and de-energized, even if one (or more) of the ground side switches has a single-point fault, by controlling the power supply side switch to open. In this manner, the driving circuit can reduce the number of components necessary for driving the coils, while the driving circuit ensures sufficient functional safety of the electromagnetic switching devices. Hereby, the “ground potential” of the driver circuit is usually defined by the low potential of a power source serving as the power supply for the driver circuit, while the potential of the “power supply side” is usually defined by the high potential of the power source serving as the power supply for the driver circuit . Accordingly, the “ground side” of the driver circuit may also be signified as “low side” of the driver circuit and the “power supply side” of the driver circuit may also be signified as “high side”.

[0012] According to a second aspect of the present disclosure, the power supply side circuit comprises a voltage converter circuit for converting an input voltage provided by a power supply into an output voltage, which is supplied to at least one of the coils of the plurality of electromagnetic switching devices, and wherein the voltage converter circuit includes the power supply side switch.

[0013] The use of a common voltage converter for supplying the required pick-up currents and the required hold-currents to a plurality of coils of electromagnetic switching devices allows the driving circuit to dispense with the need of providing individual PWM circuits for each coil. Accordingly, it is possible to lower the cost, and the board space of the driving circuit. Furthermore, the implementation of a voltage converter as a common power supply for the connected coils is advantageous in terms of electromagnetic interference, since both the number of switching circuits are reduced and also the switching loop size is reduced significantly, because the inductor of the (DCDC) voltage converter is a local component, which is placed, for example on a PCBA close to the power switch of the (DCDC) voltage converter, contrary to a contactor coil, which is placed in a harness as the inductance of a PWM switched circuit. The energy efficiency of the driving circuit according to the present disclosure is at least comparable or even improved compared to known driving circuits since the local control loop can be run faster than a PWM loop through the contactor coil, allowing for more precise and fast control. While a PWM control circuit is typically run at a switching frequency smaller than 100 kHz, a DCDC voltage converter can easily run with a switching frequency equal to or higher than 500 kHz. The additional on-board inductor and DCDC controller is outweighed when more than one (contactor) coil is supplied by the output voltage of the voltage converter.

[0014] According to a third aspect, the control circuit is configured to control the output voltage of the voltage converter circuit, such that the coils of the plurality of electromagnetic switching devices are supplied with the hold-on current, when at least one of the plurality of electromagnetic switching devices is held in the closed state and when none of the plurality of electromagnetic switching devices is switched from the open state into the closed state.

[0015] In this manner, the energy efficiency of the driving circuit can be further enhanced, because for holding the electromagnetic switching device driven by the driving circuit closed only the hold-on current, which is lower than the pick-up current, is supplied by the voltage converter to the coils connected to the driving circuit.

[0016] According to a fourth aspect, the control circuit is configured to control the output voltage of the voltage converter circuit, such that the coils of the plurality of electromagnetic switching devices are supplied with the pick-up current, when at least one of the plurality of electromagnetic switching devices is switched into the closed state. In this manner, for example a “Pass-Through” operation of the voltage converter can be implemented by regulating the output voltage of the voltage converter to correspond to the input voltage of the voltage converter for supplying the pick-up current to the connected coils. Consequently, the current rating of the storing inductor can be minimized, because during the “Pass-Through” operation the storing inductor can be used in the saturation region as no switching voltage is applied to the storing inductor.

[0017] According to a fifth aspect, the driving circuit further comprises a bypass switch, which is electrically connected in parallel to the voltage converter circuit for optionally bypassing the voltage converter circuit by closing the bypass switch, and the control circuit is configured to close the bypass switch for bypassing the voltage converter circuit, when at least one of the plurality of electromagnetic switching devices is switched into the closed state.

[0018] In this manner, the voltage converter is only used for supplying the hold-on current to the connected coils, while the higher pick-up current is supplied to the connected coils directly from the output voltage of the power supply by bypassing the voltage converter through the bypass switch. Consequently, the electronic components of the voltage converter need to be rated only for the voltages generated when supplying the hold-on current to the connected coils. This has the effect of drastically reducing the required current rating of the components of the voltage converter, especially of the switch(es) and inductor(s) of the voltage converter.

[0019] According to a seventh aspect, a plurality of current detection elements are respectively connected in series with each of the plurality of ground side switches, and the control circuit is adapted to determine the coil currents flowing through the plurality of current detection elements, and to regulate the output voltage of the voltage converter circuit in response to the detected coil currents.

[0020] In this manner, the control circuit can receive a feedback of the coil currents supplied to each of the plurality of coils and can optimize the output voltage of the voltage converter in accordance with the determined coil currents. Accordingly, the output voltage of the voltage converter can be optimized to be high enough when providing the hold current, while minimizing the losses.

[0021] According to an eighth aspect, the control circuit is adapted to regulate the output voltage of the voltage converter circuit such that a minimal difference between each of the coil currents and a respective pre-set hold-on current is larger than a predetermined positive first residual value, when the coils are supplied with the hold-on current. In an optional implementation of the eighth aspect, the control circuit is adapted to regulate the output voltage of the voltage converter circuit such that a minimal difference between each of the coil currents and a respective pre-set pick-up current is larger than a predetermined positive second residual value, when the coils are supplied with the pick-up current.

[0022] In this manner, the driving circuit can ensure that the voltage output, when supplying the hold current to the connected coils, is defined by the minimum required hold current for each contactor, so as to further maximize the energy efficiency of the driving circuit. Similar, the driving circuit can ensure that the voltage output, when supplying the pick-up current to the connected coils, is defined by the minimum required pick-up current for each contactor, so as to further maximize the energy efficiency of the driving circuit. Furthermore, the connected coils are not be damaged or experience a thermal issue, since the output voltage of the power supply is the rated voltage of the connected coils.

[0023] According to a ninth aspect, the control circuit controls the output voltage of the voltage converter circuit to be equal to a predetermined first voltage value, when the coils are supplied with the hold- on current, and to be equal to a predetermined second voltage value, which is larger than the first voltage value, when the coils are supplied with the pick-up current.

[0024] By setting predetermined voltage levels for the output voltage of the voltage converter for supplying the hold current and / or the pick-up current the energy efficiency of the driving circuit can be optimized, while at the same time the need for a measurement of the coil currents can be dispensed, so that the design of the driving circuit can be simplified.

[0025] According to a tenth aspect, the control circuit controls the power supply side switch (i) to be closed, when at least one coil of the plurality of electromagnetic switching devices is to be supplied with power, or (ii) to be open, when the coils of the plurality of electromagnetic switching devices are to be prevented from power supply, and the control circuit is configured to supply individual pulse width modulated signals to each of the plurality of ground side switches, wherein a duty cycle of each of the individual pulse width modulated signals is adjusted to individually supply the coils of the plurality of electromagnetic switching devices with the pick-up current or with the hold- on current.

[0026] In this manner, the energy efficiency of the driving circuit is optimized by controlling the coil currents, which are supplied to the connected coils of electromagnetic switching devices individually through the plurality of ground side switches. By providing a common power supply side switch for all coils (e.g. contactor coils) electrically connected to the driving circuit, it is possible to unify the power supply for all connected coils. Furthermore, the driving circuit provides sufficient functional safety for the electromagnetic switching devices, because the connected coils can be safely disconnected and de-energized, even if one (or more) of the ground side switches has a singlepoint fault, by controlling the power supply side switch to open or, when the power supply side switch has a single-point fault, by controlling plurality of ground side switches to open.

[0027] According to an eleventh aspect, the driving circuit further comprises a communication interface, through which the control circuit can receive control signals from an external control circuit, and the control signals comprise at least one of a command to close at least one of the plurality of electromagnetic switching devices, a command to open at least one of the plurality of electromagnetic switching devices, a current setpoint for the pick-up current for at least one of the coils of the plurality of electromagnetic switching devices; and a current setpoint for the hold-on current for at least one of the coils of the plurality of electromagnetic switching devices.

[0028] In this manner, an external controller can open and close the electromagnetic switches controlled by the driving circuit and can optimized the current setpoints and / or voltage setpoints, which are used for determining the output voltage of the voltage converter supplied to the connected coils.

[0029] According to a twelfth aspect, the control circuit is configured to control the plurality of electromagnetic switching devices to be opened, if the control circuit determines that control signals have not been received by the communication interface for a time interval larger than a predetermined selfdisconnection time.

[0030] In other words, the driving circuit may comprise a timeout feature that opens the controlled electromagnetic switching devices automatically a predetermined time (e.g. a few ms) after not receiving a valid command through the communication interface. Accordingly, the controlled electromagnetic switching devices can be brought into a safe state, after a hardware fault in a main controller, like a BMS microcontroller, of a power supply system, which uses the driving circuit, has occurred.

[0031] According to a thirteenth aspect, there is provided a battery management system, which comprises the driving circuit according to one of the first to twelfth aspect.

[0032] According to a fourteenth aspect, there is provided a driving method for driving coils of a plurality of electromagnetic switching devices. The driving method comprises controlling the switching of a power supply side switch for controlling power supply of the coils of the plurality of electromagnetic switching devices, controlling switching of each of a plurality of ground side switches, which respectively are adapted to connect one of the coils of the plurality of electromagnetic switching devices to a ground potential. Hereby, the switching of the power supply side switch and the switching of the plurality of ground side switches is controlled to individually supply the coils of the plurality of electromagnetic switching devices at least with a pick-up current for switching the respective one of the plurality of electromagnetic switching devices from an open state into a close state, or a hold-on current for holding the respective one of the plurality of electromagnetic switching devices in the close state.

[0033] According to a fifteenth aspect, the power supply side switch is part of a voltage converter circuit, which converts an input voltage provided by a power supply into an output voltage. The driving method further comprises controlling the output voltage of the voltage converter circuit by controlling switching of the power supply side switch such that the coils of the plurality of electromagnetic switching devices are supplied with the hold-on current, when at least one of the plurality of electromagnetic switching devices is held in the closed state and when none of the plurality of electromagnetic switching devices is switched into the closed state, and the coils of the plurality of electromagnetic switching devices are supplied with the pick-up current, when at least one of the plurality of electromagnetic switching devices is switched into the closed state.

[0034] According to a sixteenth aspect, an integrated circuit is provided (that may be deployed in a battery management system). The integrated circuit, in operation, controls a process of a driving circuit, the process including the steps of the method according to one of the fourteenth or fifteenth aspects.

[0035] Throughout this document, the term “terminal” is meant to describe a point at which a conductor from an electric device, an electric circuit or an electric component ends, and where a point is provided for electrically connecting an external electric device, an external electric circuit or an external electric component to this conductor. The term “node” may refer to a point where the terminals of one or more circuit components meet or may refer to the entire wire, which conduc- tively couples the terminals of one or more electric circuit components. Further, the terms “electrically connected” and “conductively coupled” describe the establishing of an electrical connection between at least two electric devices, electric components or electric conductors, which allows the flow of electric current. Hereby the electrical connection should not be restricted to a direct coupling of the terminals of the at least two electric devices, electric components or electric conductors, but other electric devices, electric components or electrical conductors may be coupled in between.

[0036] The accompanying drawings are incorporated into the specification and form a part of the specification to illustrate several examples of the present disclosure. These drawings, together with the description serve to explain the principles of the disclosure. The drawings are merely for the purpose of illustrating the preferred and alternative examples of how the disclosure can be made and used, and are not to be construed as limiting the disclosure to only the illustrated and described examples. Furthermore, several aspects of the examples may form — individually or in different combinations — solutions according to the present disclosure. The following described examples thus can be considered either alone or in an arbitrary combination thereof. Further features and advantages will become apparent from the following more particular description of the various examples of the disclosure, as illustrated in the accompanying drawings, in which like references refer to like elements, and wherein:

[0037] FIG. 1 shows a schematic circuit diagram of a first exemplary driving circuit;

[0038] FIG. 2 shows a schematic circuit diagram of a second exemplary driving circuit;

[0039] FIG. 3 shows another schematic circuit diagram of the second exemplary driving circuit;

[0040] FIG. 4 shows another schematic circuit diagram of the second exemplary driving circuit;

[0041] FIG. 5 shows a schematic circuit diagram of a third exemplary driving circuit;

[0042] FIG. 6 shows a schematic circuit diagram of a known contactor coil driving circuit.

[0043] The present disclosure will now be further explained referring to the Figures. Fig. 1 shows a schematic circuit diagram of a first exemplary driving circuit 100. The exemplary driving circuit 100 is configured to energize coils 21 , 22, 23 of a plurality of corresponding electromagnetic switching devices, depending on the intended states of the electromagnetic switching devices, i.e. depending on whether the corresponding electromagnetic switching devices are intended to be open in an OFF state (or non-conducting state), to be closed in an ON state (or conducting state) or switched between the OFF and ON state or vice versa. The exemplary driving circuit 100 comprises a power supply side circuit (or high side circuit), which is connectable by a first terminal 102 to coils 21 , 22, 23 of a plurality of electromagnetic switching devices, and a ground side circuit (or low side circuit), which is connectable by a plurality of second terminals 104 to the coils 21 , 22, 23. Hereby, respectively one of the second terminals 104 is electrically connected to one of the coils 21 , 22, 23.

[0044] The power supply side circuit is configured to electrically connect the coils 21 , 22, 23 to a power supply, which serves as a power source to energize the coils 21 , 22, 23. For example, the power supply side circuit can be connected by a power connection terminal 106 to an external power supply, like the low voltage battery (auxiliary battery) of an electric vehicle, which supplies a voltage at a low voltage level, e.g., of 12 V, 24 V, 48 V or similar. Alternatively, the power supply side circuit may be supplied directly by an internal power supply, like the high voltage battery of an electric vehicle, which supplies a voltage at a high voltage level of, e.g., 200 V, 400 V, 800 V or similar. In this case the power supply side circuit may comprise suitable electronics for converting the high voltage to a voltage suitable for the components of the power supply side circuit. The ground side circuit is configured to electrically connect each of the coils 21 , 22, 23 separately to a ground potential, which is, for example, defined by the low side potential of the power supply.

[0045] For controlling the energization of the plurality of coils 21 , 22, 23, the power supply side circuit comprises a power supply side switch 108, which is electrically connected between the first terminal 102 and the power connection terminal 106 and allows a control circuit (not shown in Fig. 1) of the driving circuit 100 to collectively control power supply of the coils 21 , 22, 23. Further, in order to individually control power supply of each of the coils 21 , 22, 23, the ground side circuit comprises a plurality of ground side switches 110, which each are electrically connected between one of the plurality of second terminals 104 and the ground potential. With this configuration, it is possible to collectively switch on and off the power supply of the coils 21 , 22, 23 on the high potential side by closing and opening the common power supply side switch 108, while it is possible to switch on and off power supply for each coil 21 , 22, 23 individually, by closing and opening the plurality of ground side switches 110.

[0046] The power supply side switch 108 and the plurality of ground side switches 110 may be semiconductor switches, in particular transistors, like IGBTs or MOSFETs. The power supply side switch 108 and the plurality of ground side switches 110 are controlled by a control circuit (not shown in Fig. 1) of the driving circuit 100. The control circuit may have the form of an integrated circuit (IC), or, for example, may be realized by a processor, a microcontroller or similar. The control circuit switches the power supply side switch 108 and the plurality of ground side switches 110 on and off, such that the coils 21 , 22, 23 are individually supplied with at least one of a pick-up current for switching the respective one of the plurality of electromagnetic switching devices from an open state into a close state and a hold-on current for holding the respective one of the plurality of electromagnetic switching devices in the close state.

[0047] As illustrated in Fig.1 , the power supply side switch 108 is part of a voltage converter circuit 112. The voltage converter circuit 112 is included in the power supply side circuit and is configured to convert an input voltage, which is provided by the power supply and is applied across the input capacitor 114 of the voltage converter circuit 112, into an output voltage, which is applied across the output capacitor 116 of the voltage converter circuit 112. The output voltage is supplied to the coils 21 , 22, 23, so that the voltage converter circuit 112 can work as a constant voltage source with adjustable voltage for each of the coils 21 , 22, 23. In the illustrated example, the voltage converter circuit 112 is a non-isolated switch mode power supply for the coils 21 , 22, 23.

[0048] In particular, for applications, where the input voltage is always higher than the required output voltage, the voltage converter circuit 112 can advantageously have a buck converter topology, like a synchronous or asynchronous buck converter. In the asynchronous buck converter topology, the voltage converter circuit 112 comprises a storing inductor 118 as an energy storage element, which is electrically connected in series with the power supply side switch 108, and a unidirectional switch 120, like a diode which is arranged to allow current flow from the ground potential into the storing inductor 118, but blocks current flow in the opposite direction. In the synchronous buck converter topology, the unidirectional switch 120 is replaced by an additional semiconductor switch, such as a MOSFET. Alternatively, for applications, where the input voltage may temporarily fall below the required output voltage, for example due to transients or to power supply interruptions, the voltage converter circuit 112 can advantageously have a buck-boost converter topology, like a four switch buck-boost converter, so that the coils 21 , 22, 23 can be kept energized even if the input voltage temporarily falls below the required output voltage.

[0049] The control circuit of the first exemplary driving circuit 100 controls the switching of the power supply side switch 108, which regulates the output voltage of the voltage converter circuit 112, and the switching of the plurality of ground side switches 110 according to the following control method.

[0050] The plurality of ground side switches 110 are switched individually to be either conducting or nonconducting, depending on the desired states of the corresponding electromagnetic switching devices. For example, when the electromagnetic switching device, which is actuated by a magnetic field generated by the coil 21 , should be in the OFF state or switched from the ON state to the OFF state, the ground side switch 110, which is electrically connected in series with the coil 21 , is opened by the control circuit. Otherwise, when the electromagnetic switching device, which is actuated by a magnetic field generated by the coil 21 , should be in the ON state or switched from the OFF state to the ON state, the ground side switch 110, which is electrically connected in series with the coil 21 , is closed by the control circuit. In an analog manner, the ground side switch 110, which is electrically connected in series with the coil 22, is opened and closed by the control circuit, depending on the intended state of the electromagnetic switching device, which is actuated by the magnetic field generated by the coil 22, and the ground side switch 110, which is electrically connected in series with the coil 23, is opened and closed by the control circuit, depending on the intended state of the electromagnetic switching device, which is actuated by the magnetic field generated by the coil 23.

[0051] The power supply side switch 108 is switched by the control circuit to regulate the output voltage of the voltage converter circuit 112 depending on the intended states of the plurality of electromagnetic switching devices, which are actuated by the coils 21 , 22, 23 being supplied by the output voltage of the voltage converter circuit 112.

[0052] When all of the plurality of electromagnetic switching devices are in the OFF state, i.e. when none of the coils 21 , 22, 23, which are connected to the driving circuit 100 are to be energized, the power supply side switch 108 is opened by the control circuit to interrupt power supply to the coils 21 , 22, 23.

[0053] When at least one of the plurality of electromagnetic switching devices is to be switched from the OFF state to the ON state, the control circuit controls the voltage converter circuit 112 to work in a “pull-in” state, where a pick-up current is supplied to the coils 21 , 22, 23. In the “pull-in” state, the power supply side switch 108 is opened and closed by the control circuit with a switching frequency that results in an output voltage of the voltage converter circuit 112 that is large enough to supply the pick-up current to the coils 21 , 22, 23. In the simplest implementation, the power supply side switch 108 is simply kept closed by the control circuit for supplying the pick-up current to the coils 21 , 22, 23, so that the output voltage of the voltage converter circuit 112 is substantially equal to the input voltage of the voltage converter circuit 112. In this manner, a “Pass-Through” operation of the voltage converter circuit 112 is implemented, wherein the current rating of the storing inductor 118 can be minimized, because during the “Pass-Through” operation the storing inductor 118 can be used in the saturation region as no switching voltage is applied to the storing inductor 118. Alternatively, in the “pull-in” state, the output voltage of the voltage converter circuit 112 may be controlled to be below the input-voltage supplied by the power source. In particular, in the “pull-in” state the output voltage of the voltage converter circuit 112 may be set depending on the required “pull-in” voltages Vpuiiin,n of the n coils 21 , 22, 23 as

[0054] In equation (1), VDCDC.OUI is the output voltage of the voltage converter circuit 112 in the “pull-in” state, max(VPuiiin,n) describes the maximum “pull-in” voltage among the “pull-in” voltages required for the coils, electrically connected to the voltage converter circuit 112, to close the corresponding electromagnetic switch devices, and Vthreshoid describes a threshold, which can be calibrated.

[0055] When at least one of the plurality of electromagnetic switching devices is to be held in the ON state and when none of the plurality of electromagnetic switching devices is to be switched from the OFF state to the ON state, the control circuit controls the voltage converter circuit 112 to work in a “hold-on” state, where a hold-on current is supplied to the coils 21 , 22, 23. In the “hold-on” state, the power supply side switch 108 is opened and closed by the control circuit with a switching frequency that results in an output voltage of the voltage converter circuit 112 that is large enough to supply the hold-on current to the coils 21 , 22, 23. Since the hold-on current required for the coils

[0056] 21 , 22, 23 to hold the corresponding electromagnetic switching devices in the ON state is lower than the pick-up currents required for the required for the coils 21 , 22, 23 to switch the corresponding electromagnetic switching devices from the OFF state to the ON state, the output voltage of the voltage converter circuit 112 is set in the “hold-on” state to a lower voltage level than the output voltage of the voltage converter circuit 112 is set in the “pull-in” state. For example, in the “hold- on” state, the output voltage of the voltage converter circuit 112 may be set depending on the required “hold-on” voltages Vhoid.n of the n coils 21 , 22, 23 as

[0057] In equation (2), VDCDC.OUI is the output voltage of the voltage converter circuit 112 in the “hold-on” state, max(Vhoid,n) describes the maximum “hold-on” voltage of the coils, electrically connected to the voltage converter circuit 112, to keep the corresponding electromagnetic switching devices closed, and Vthreshoid describes a threshold, which can be calibrated.

[0058] For further reducing the energy consumption of the coils 21 , 22, 23 in the “pull-in” state and in the “hold-on” state, the control circuit may alternatively use a closed loop control method (in contrast to the open loop control method described above) and regulate the output voltage of the voltage converter in response to coil currents, which are determined individually for each of the coils 21 ,

[0059] 22, 23. For this purpose, the ground side circuit comprises a plurality of current detection elements 122, which are respectively connected in series with one of the plurality of ground side switches 110. In the illustrated exemplary implementation, the current detection elements 122 have the form of shunt resistors, but also other current detection elements 122 known in the art can be used, for example hall sensors. Further, in the illustrated exemplary implementation, the control circuit comprises current detection circuitry, which detects the voltages dropping across the current detection elements 122 by using the voltage taps 124. The control circuit determines a current flowing through each of the coils 21 , 22, 23 on the basis of the output of the current detection circuitry.

[0060] In the “pull-in” state, the control circuit determines a residual current lresiduai as control variable by the following equation (3)

[0061] ^residual ITlin( / nIpullin,n ■ (3)

[0062] Accordingly, in the “pull-in” state lresiduai is the minimal difference between the actually determined pull-in current Ipuiiininand the required pull-in current ln, respectively determined for each of the coils 21 , 22, 23, which are switching a corresponding electromagnetic switch from the OFF state into the ON state (i.e. for all coils, which actuating an electromagnetic switch to become closed). The control circuit then regulates, for example, by means of an integrated proportional-integral- derivative (PID) controller, the residual current lresiduai to become equal to a predetermined positive value, so that it is ensured that in the “pull-in” state the pick-up current is large enough for closing the electromagnetic switch devices.

[0063] In the “hold-on” state, the control circuit determines the residual current lresiduai as control variable by the following equation (4)

[0064] ^residual ITlin( / nIhold,n - (4)

[0065] Accordingly, in the “hold-on” state lresiduai is the minimal difference between the actually determined hold current Ihoid,nand the required hold current ln, respectively determined for each of the coils 21 , 22, 23, which are connected to the driving circuit 100, individually. The control circuit then regulates, for example by a PID controller, the residual current lresiduai to become equal to a predetermined positive value, so that it is ensured that in the “hold” state the hold current is large enough to keep the electromagnetic switch devices close.

[0066] By the above-described closed loop feedback control method, it is possible to optimize the regulation of the output voltage of the voltage converter circuit 112 such that the current consumption of the coils is minimized at least in the “hold state”, where the respective electromagnetic switches are kept close. This effect is also achieved, if for the “pull-in” state a predetermined output voltage is set, and the closed loop feedback control is only applied in the “hold on” state.

[0067] When one (or more) of the plurality of electromagnetic switch devices is intended to be opened, i.e. intended to be switched from its ON state to its OFF state, the corresponding one (or more) of the coils 21 , 22, 23 should be de-energized quickly. For this purpose, each of the ground side switches 110 is electrically connected in parallel with a clamping device 126, which is configured to clamp the low potential side of the coils to a potential defined by the clamping device. This allows to de-energize each of the coils 21 , 22, 23 quickly, by respectively opening the ground side switch(es) 110, which is (are) electrically connected in series with the coil(s) to be de-energized, and clamping the low potential of the coil(s) to be de-energized to the potential defined by the clamping device 126. As an example, the clamping devices 126 can be realized by transient- voltage-suppression (TVS) diodes, which are connected in parallel to the ground side switches 110 and provide a clamping voltage of, for example, 40 V or higher, so that voltage spikes, which are generated by the coils 21 , 22, 23, when opening the ground side switches 110, can be suppressed by the TVS diodes. As another implementation option, instead of using a discrete clamping device, it is also possible to use semiconductor switches, which have integrated clamping diodes, as the ground side switches 110. Similarly, it is possible to implement a clamping device in the power supply side circuit to clamp the high potential side of the coils to a potential, for example, 40 V or higher, defined by the clamping device of the power supply side circuit. This allows to suppress voltage spikes, which are generated by the coils 21 , 22, 23, when opening the power supply side switch 108, and to de-energize the coils 21 , 22, 23 quickly, when opening the power supply side switch 108.

[0068] Furthermore, the voltage converter 112 may be advantageously designed such that losses during the time where the voltage converter circuit 112 is switched off are minimal, for example during the time where all electromagnetic switch devices controlled by the driving circuit 100 are opened (i.e. in the OFF state). In an optional implementation, the voltage converter 112 may be designed to be current limited and may limit the current supplied to the coils 21 , 22, 23 to a predetermined maximum current value. Alternatively or in addition, additional current limiting devices may be integrated with each of the ground side switches 110.

[0069] By the above-described design, the first exemplary driving circuit 100 achieves sufficient functional safety by allowing to electrically connect each of the coils 21 , 22, 23 in series with the common power supply side switch 108, which is part of the voltage converter circuit 112, and respectively with one of the ground side switches 110. Accordingly, the coils 21 , 22, 23 can be safely disconnected and de-energized, even if one (or more) of the ground side switches 110 has a single-point fault, by controlling the power supply side switch 108 to open for interrupting the power supply to the coils 21 , 22, 23. Similar, the coils 21 , 22, 23 can be safely disconnected and de-energized, even if the power supply side switch 108 or another component of the voltage converter circuit 112 has a single-point fault, by controlling the plurality of ground side switches 110 to open for interrupting the power supply to the coils 21 , 22, 23. Consequently, with the above-described design of the first exemplary driving circuit 100, it becomes obsolete to present individual power supply side switches and ground side switches for each of the coils 21 , 22, 23.

[0070] Figs. 2-4 show schematic circuit diagrams of a second exemplary driving circuit 200. The second exemplary driving circuit 200 has a similar design and a similar functioning as the first exemplary driving circuit 100, so that explanations of components and their functions, which have been already explained for the first exemplary driving circuit 100, will be omitted in the following. The second exemplary driving circuit 200 in addition to the first exemplary driving circuit 100 comprises a bypass switch 228 as a part of the power supply side circuit. The bypass switch 228 is electrically connected in parallel to the voltage converter circuit 112, and in particular to the power supply side switch 108 of the voltage converter circuit 112, at nodes 230 and 232, so that by closing the bypass switch 228, the control circuit of the second exemplary driving circuit 200 can bypass the voltage converter circuit 112. Especially, the bypass switch 228 provides a direct electric connection between the power connection terminal 106 and the first terminal 102, so that the coils 21 , 22, 23 can be directly supplied from the output voltage of the power supply, when the bypass switch 228 is closed.

[0071] To avoid current flow from the bypass switch 228 to the voltage converter circuit 112, when the bypass switch 228 is closed, a protection device 234 is electrically connected in series to the voltage converter circuit 112 between the voltage converter circuit 112 and the node 232. For example, a unidirectional switch, like a diode, which only allows current flow from the voltage converter circuit 112 to the node 232 may be used as the protection device 234. Alternatively, a semiconductor switch, which is closed, when the bypass switch 228 is opened, may be used as the protection device 234.

[0072] For supplying the pick-up current to the coils 21 , 22, 23, which are electrically connected to the second exemplary driving circuit 200, the control circuit opens the power supply side switch 208 and closes the bypass switch 228, so the connected coils 21 , 22, 23 are directly supplied by the power supply, to which the second exemplary driving circuit 200 is electrically connected. For supplying the hold-on current to the coils 21 , 22, 23, which are electrically connected to the second exemplary driving circuit 200, the control circuit opens the bypass switch 228 and controls the voltage converter circuit 112 to work in the “hold-on” state, where a hold-on current is supplied to the coils 21 , 22, 23 by opening and closing the power supply side switch 108 in the same manner as described for the first exemplary driving circuit 100. Especially, the control circuit may use one of the open loop control method or the closed loop control method, which were described before, for controlling the output voltage of the voltage converter circuit 112 to supply the hold-on current to the coils 21 , 22, 23.

[0073] Because in the second exemplary driving circuit 200, the voltage converter circuit 112 is only driven in the “hold-on” state, while for supplying the higher pick-up current the voltage converter circuit 112 is bypassed through the bypass switch 228, the components of the voltage converter circuit 112 of the second exemplary driving circuit 200 need to be rated only for the voltages generated in the “hold-on” state. This has the advantageous effect of drastically reducing the required current rating of the components of the voltage converter circuit 112, especially of the switches and inductors of the voltage converter circuit 112.

[0074] Fig. 3 shows an application example, where the second exemplary driving circuit 200 is configured to drive the coils of three different electromagnetic switching devices. In this application example, the pick-up current is supplied to the coils 21 , 22, 23 by closing the bypass switch 228 and the respective ground side switches 110. The hold-on current is supplied to the coils 21 , 22, 23 by opening the bypass switch 228 and supplying the coils with the output voltage of the voltage converter circuit 112, and by closing the respective ground side switches 110. Here, the output voltage of the voltage converter circuit 112 is controlled by the control circuit with the closed loop feedback control, by taking into account the actual hold-on currents, which are detected by means of the current detection elements 122.

[0075] As exemplary illustrated in Fig.4, the control circuit of the second exemplary driving circuit 200 (and the first exemplary driving circuit 100) may comprise a communication circuit 438, which allows the control circuit to receive control signals from an external controller, like a controller of a battery management system (BMS) or an electronic control unit (ECU) of a vehicle. The communication circuit 438 communicates with the external controller, for example, by an i2C (Inter-Integrated Circuit) communication protocol, an SPI (Serial Peripheral Interface) communication protocol, digitally or with another suitable communication interface known in the art, such as a PWM signal, to receive control instructions.

[0076] For example, the control circuit can receive from the external controller commands to close and / or to open one (or more) of the plurality of electromagnetic switching devices and can then control switching the power supply side switch 108, the bypass switch 228 and the plurality of ground side switches 110 in response to the received commands. In addition or alternatively, the control circuit can receive from the external controller a current setpoint for the hold-on current for one or more of the coils 21 , 22, 23, so that the external controller can ensure that the voltage converter circuit 112 supplies the desired hold-on currents to each of the coils 21 , 22, 23 in the “hold-on” state. In applications, where the bypass switch 228 is not included, the control circuit can receive from the external controller a current setpoint for the pick-up current for one or more of the coils 21 , 22, 23, so that the external controller can ensure that the voltage converter circuit 112 supplies the desired pick-up currents to each of the coils 21 , 22, 23 in the “pull-in” state. In applications, where the control circuit uses the open-loop feedback control method of the output voltage of the voltage converter instead of the closed loop feedback control method of the coils currents, the control circuit can receive from the external controller a voltage setpoint for the output voltage of the voltage converter circuit 112 in the “hold-on” state and / or in the “pull-in” state.

[0077] For enhancing the functional safety of the controlled electromagnetic switch devices, the control circuit of the second exemplary driving circuit 200 (and of the first exemplary driving circuit 100) may further provide a configurable timeout function. The timeout function may be implemented by controlling the power supply side switch 108, and the plurality of ground side switches 110 (and eventually the bypass switch 228) to open, if the communication circuit 438 does not receive a communication signal from the external controller for a predetermined time (“self-disconnection time”), because in this case a malfunction and / or a stop of operation of the external controller is assumed. This can ensure that the electromagnetic switch devices are safely opened after a fault in the main controller of a power supply system has happened. In particular, when the timeout function is performed, the control circuit may control the coils 21 , 22, 23 to be de-energized after a predetermined time (e.g. within a few ms), so that the electromagnetic switch devices are forced to open, or may control the coils 21 , 22, 23 to be de-energized after it is ensured that the current through the electromagnetic switch devices is low enough for a safe opening.

[0078] Notably, with the driving methods, which are performed by the control circuit of the first exemplary driving circuit 100, and with the driving methods, which are performed by the control circuit of the second exemplary driving circuit 200, all coils 21 , 22, 23, which are electrically connected to the driving circuit and for which the respective ground side switch 110 is closed, are supplied with the pick-up current, even if some of the coils 21 , 22, 23 belong to already closed electromagnetic switch devices, during the closing of one of the electromagnetic switching device. Accordingly, for the brief period of pull-in, the electromagnetic switching devices, which are in hold state, will also draw a higher amount of current. However, since the time during which the electromagnetic switching devices are kept closed (the time where the driving circuits 100 and 200 drive the coils 21 , 22, 23 in the “hold-on” state) is significantly higher than the time during which the electromagnetic switching devices are brought into the closed state (the time where the driving circuits 100 and 200 drive the coils 21 , 22, 23 in the “pick up” state), the overall energy consumption is only mar- ginally increased. For example, for a typical time of 150 ms for closing an electromagnetic switching device and for a pick up current that is equal to four times the hold current, the power consumption increases by only 0.017% per closing event of an electromagnetic switch device.

[0079] Furthermore, in the described implementation examples, it is assumed that a same type of electromagnetic switching devices is driven by a single driving circuit, so that it can be expected that the required hold currents, e.g. I_hold_21 , l_hold_22, and l_hold_23 of the three exemplary coils 21 , 22 and 23 are identical or very similar. As a consequence also the required “hold-on” voltage will be very similar for the three exemplary coils 21 , 22 and 23. But the above described driving circuits also work well for controlling power supply of coils from different electromagnetic switching devices, because even if the required hold currents l_hold_21 , l_hold_22, and l_hold_23 differ between types of electromagnetic switching devices, the associated “hold-on” voltage are very close to each other, since coils of electromagnetic switching devices, which require lower hold currents, typically have a higher coil resistance.

[0080] Fig. 5 shows a schematic circuit diagrams of a third exemplary driving circuit 300, which varies in design from the first exemplary driving circuit 100 and from the second exemplary driving circuit 200, in that the power supply side circuit of the third exemplary driving circuit 300 does not comprise the voltage converter circuit 112, but only comprises a power supply side switch 308 electrically connected between the first terminals 102 and the power connection terminal 106 (not shown in Fig.5).

[0081] The control circuit of the third exemplary driving circuit 300 controls the switching of the power supply side switch 308 only to enable or interrupt power supply of the coils 21 , 22, 23 from the power supply 336, but not for altering the output voltage of the power supply 336 (as the voltage converter circuit 112 does). This means that the control circuit of the third exemplary driving circuit 300 controls the power supply side switch 308 to be closed when at least one of the coils 21 , 22, 23 is to be energized (to close or hold close the corresponding electromagnetic switch device) and controls the power supply side switch 308 to be open when none of the coils 21 , 22, 23 is to be energized (to open or hold open the corresponding electromagnetic switch device) or when a single point fault occurs in one of the coils 21 , 22, 23 or one of the ground side switches 310.

[0082] To regulate the currents supplied to the currents in the coils 21 , 22, 23, the control circuit of the third exemplary driving circuit 300 individually controls the switching of the ground side switches 310. In particular, the control circuit of the third exemplary driving circuit 300 controls those one of the ground side switches 310 to be open, which are electrically connected in series with coils of electromagnetic switch devices that are to be opened or to be hold open. Further, the control circuit of the third exemplary driving circuit 300 controls those one of the ground side switches 310, which are electrically connected in series with coils of electromagnetic switch devices that are to be hold in the closed state, to be alternately open and closed with a specific first duty cycle, which enables reducing the current provided to those coils to correspond to a corresponding hold- on current. Hereby, the hold-on current and the required first duty cycle may be determined by the control circuit of the third exemplary driving circuit 300 in analogous manner as described for the first exemplary driving circuit 100 and for the second exemplary driving circuit 200, but here, the hold-on current (or the corresponding “hold-on” voltage) is determined individually for each coil 21 , 22, 23 and not from a minimum difference of all the current branches. Further, the control circuit of the third exemplary driving circuit 300 controls those one of the ground side switches 310, which are electrically connected in series with coils of electromagnetic switch devices that are to be switched from the open state in the closed state, to be alternately open and closed with a specific second duty cycle, which is smaller than the first duty cycle and enables the current provided to those coils to be sufficiently large for closing the corresponding electromagnetic switch devices. For example, for supplying the pick-up current, to any of the coils 21 , 22, 23, the control circuit of the third exemplary driving circuit 300 may control the corresponding ground side switches 310 closed, so that the complete output voltage of the power supply 336 is applied.

[0083] Similar to the first exemplary driving circuit 100 and to the second exemplary driving circuit 200, the third exemplary driving circuit 300 may also comprise the communication circuit 438, which allows the control circuit to receive control signals from an external controller. In particular, the controller of the third exemplary driving circuit 300 may receive from the external controller commands to close and / or to open one (or more) of the plurality of electromagnetic switching devices from the external controller and / or current setpoints for the pick-up current and / or for the hold-on current for one or more of the coils 21 , 22, 23. The control circuit of the third exemplary driving circuit 300 can then control the switching of the power supply side switch 308 and of the plurality of ground side switches 310 in accordance with the received control signals. Furthermore, the control circuit of the third exemplary driving circuit 300 may provide a configurable timeout function (as described above for the control circuit of the first exemplary driving circuit 100 and of the second exemplary driving circuit 200) to enhance the functional safety of the controlled electromagnetic switch devices.

[0084] With the driving method, which is performed by the control circuit of the third exemplary driving circuit 300, the pick-up current is selectively supplied only to those of the coils 21 , 22, 23, which are closing the corresponding electromagnetic switches, but not to those of the coils 21 , 22, 23, which are holding the corresponding electromagnetic switches in the closed state. Yet, the third exemplary driving circuit 300 achieves sufficient functional safety by allowing to electrically connect each of the coils 21 , 22, 23 in series with the common power supply side switch 308 and respectively with one of the ground side switches 310. In particular, the coils 21 , 22, 23 can be safely disconnected and de-energized, even if one (or more) of the ground side switches 310 has a single-point fault, by controlling the power supply side switch 308 to open for interrupting the power supply to the coils 21 , 22, 23. Similar, the coils 21 , 22, 23 can be safely disconnected and de-energized, even if the power supply side switch 308 has a single-point fault, by controlling the plurality of ground side switches 110 to open for interrupting the power supply to the coils 21 , 22, 23. Consequently, it becomes obsolete to present individual power supply side switches for each of the coils 21 , 22, 23.

[0085] While in Figs. 1 to 4, the first exemplary driving circuit 100 and the second exemplary driving circuit 200 are illustrated with a common first terminal 102, to which each of the plurality of the coils 21 ,

[0086] 22, 23 can be commonly electrically connected, there may be instead provided a plurality of separate first terminals 102, to which the plurality of the driven coils 21 , 22, 23 can be separately electrically connected as it is shown in Fig. 5 for the third exemplary driving circuit 300. Similar, the third exemplary driving circuit 300 may be provided with a common first terminal 102 instead of the plurality of separate first terminal 102 shown in Fig. 5 for connecting the driven coils 21 , 22,

[0087] 23.

[0088] Each of the described exemplary driving circuits may be formed as a single integrated circuit component. Hereby, the term integrated component should especially mean that all components necessary for providing the above-described functions and methods performed by the exemplary driving circuits, are packaged together as a single compact component, in particular with a common housing and a unifying substrate, so as to form the integrated circuit component. Alternatively, each of the above described circuits can be realized as a dedicated integrated circuit and the dedicated integrated circuits are assembled to form an assembled circuit. The functionalities of each circuit described above may be realized by software, hardware, or software in cooperation with hardware. Alternatively, one or more of the above described circuits may be realized by using general-purpose processors, special-purpose processors, or FPGAs (Field Programmable Gate Array) that can be programmed.

[0089] The present invention also relates to a battery management system, which comprises at least one of the above-described exemplary driving circuits for driving the coils 21 , 22, 23 of a plurality of electromagnetic switching devices. For enhancing the redundancy in the battery management system, in an exemplary implementation, more than one of the above-described exemplary driving circuits is electrically connected to the coils 21 , 22, 23. For example, it is possible to provide a battery management system with two of the exemplary driving circuits, wherein the two exemplary driving circuits control redundantly control power supply of each of the connected coils 21 , 22, 23. To enhance the redundancy, the different exemplary driving circuits implemented in the BMS should be powered from different power supplies. Accordingly, even if one of the exemplary driving circuits has a hardware fault and need to stop power supply of the connected coils 21 , 22, 23, the system can be kept operating since the remaining exemplary driving circuits are able to still supply the connected coils 21 , 22, 23 and keep the corresponding electromagnetic switches closed.

[0090] REFERENCE NUMERALS

Claims

CLAIMS1. A driving circuit (100, 200, 300) for driving coils (21 , 22, 23) of a plurality of electromagnetic switching devices, comprising: a power supply side circuit, which comprises a power supply side switch (108, 308) for controlling power supply of the coils (21 , 22, 23) of the plurality of electromagnetic switching devices, a ground side circuit, which comprises a plurality of ground side switches (110, 310), wherein each of the plurality of ground side switches (110, 310) is adapted to electrically connect one of the coils (21 , 22, 23) of the plurality of electromagnetic switching devices to a ground potential, and a control circuit for controlling the switching of the power supply side switch (108, 308) and the switching of the plurality of ground side switches (110, 310) to individually supply the coils (21 , 22, 23) of the plurality of electromagnetic switching devices at least with• a pick-up current for switching the respective one of the plurality of electromagnetic switching devices from an open state into a close state, or• a hold-on current for holding the respective one of the plurality of electromagnetic switching devices in the close state.

2. The driving circuit (100, 200, 300) according to claim 1 , wherein the power supply side circuit comprises a voltage converter circuit (112) for converting an input voltage provided by a power supply into an output voltage, which is supplied to at least one of the coils (21 , 22, 23) of the plurality of electromagnetic switching devices, and wherein the voltage converter circuit (112) circuit includes the power supply side switch (108, 308).

3. The driving circuit (100, 200, 300) according to claim 2, wherein the control circuit is configured to control the output voltage of the voltage converter circuit (112), such that the coils (21 , 22, 23) of the plurality of electromagnetic switching devices are supplied with the hold-on current, when at least one of the plurality of electromagnetic switching devices is held in the closed state and when none of the plurality of electromagnetic switching devices is switched from the open state into the closed state.

4. The driving circuit (100, 200, 300) according to one of claims 2 or 3, wherein the control circuit is configured to control the output voltage of the voltage converter circuit (112), such that the coils (21 , 22, 23) of the plurality of electromagnetic switching devices are supplied with the pick-up current, when at least one of the plurality of electromagnetic switching devices is switched into the closed state.

5. The driving circuit (100, 200, 300) according to one of claims 2 or 3, further comprising a bypass switch (228), which is electrically connected in parallel to the voltage converter circuit (112) for optionally bypassing the voltage converter circuit (112) by closing the bypass switch (228), wherein the control circuit is configured to close the bypass switch (228) for bypassing the voltage converter circuit (112), when at least one of the plurality of electromagnetic switching devices is switched into the closed state.

6. The driving circuit (100, 200, 300) according to one of claims 2 to 5, wherein the control circuit individually controls the plurality of ground side switches (110, 310) (i) to be closed, when a coil of a respective one of the plurality of electromagnetic switching devices is to be supplied by the voltage converter circuit (112), or (ii) to be open, when a coil of a respective one of the plurality of electromagnetic switching devices is to be prevented from power supply by the voltage converter circuit (112).

7. The driving circuit (100, 200, 300) according to one of claims 2 to 6, wherein a plurality of current detection elements (122) are respectively connected in series with each of the plurality of ground side switches (110, 310), and wherein the control circuit is adapted to determine the coil currents flowing through the plurality of current detection elements (122), and to regulate the output voltage of the voltage converter circuit (112) in response to the detected coil currents.

8. The driving circuit (100, 200, 300) according to claim 7, wherein the control circuit is adapted to regulate the output voltage of the voltage converter circuit (112) such that a minimal difference between each of the coil currents and a respective pre-set hold-on current is larger than a predetermined positive first residual value, when the coils (21 , 22, 23) are supplied with the hold-on current, and optionally, wherein the control circuit is adapted to regulate the output voltage of the voltage converter circuit (112) such that a minimal difference between each of the coil currents and a respective pre-set pick-up current is larger than a predetermined positive second residual value, when the coils (21 , 22, 23) are supplied with the pick-up current.

9. The driving circuit (100, 200, 300) according to one of claims 2 to 6, wherein the control circuit controls the output voltage of the voltage converter circuit (112) to be equal to a predetermined first voltage value, when the coils (21 , 22, 23) are supplied with the hold-on current, and to be equal to a predetermined second voltage value, which is larger than the first voltage value, when the coils (21 , 22, 23) are supplied with the pick-up current.

10. The driving circuit (100, 200, 300) according to claim 1 , wherein the control circuit controls the power supply side switch (108, 308) (i) to be closed, when at least one coil of the plurality of electromagnetic switching devices is to be supplied with power, or (ii) to be open, when the coils (21 , 22, 23) of the plurality of electromagnetic switching devices are to be prevented from power supply, and wherein the control circuit is configured to supply individual pulse width modulated signals to each of the plurality of ground side switches (110, 310), wherein a duty cycle of each of the individual pulse width modulated signals is adjusted to individually supply the coils (21 , 22, 23) of the plurality of electromagnetic switching devices with the pick-up current or with the hold- on current.11 . The driving circuit (100, 200, 300) according to one of the preceding claims, further comprising a communication interface, through which the control circuit can receive control signals from an external control circuit, wherein the control signals comprise at least one of the following:• a command to close at least one of the plurality of electromagnetic switching devices;• a command to open at least one of the plurality of electromagnetic switching devices;• a current setpoint for the pick-up current for at least one of the coils (21 , 22, 23) of the plurality of electromagnetic switching devices; and• a current setpoint for the hold-on current for at least one of the coils (21 , 22, 23) of the plurality of electromagnetic switching devices.

12. The driving circuit (100, 200, 300) according to claim 11 , wherein the control circuit is configured to control the plurality of electromagnetic switching devices to be opened, if the control circuit determines that control signals have not been received by the communication interface for a time interval larger than a predetermined self-disconnection time.

13. A battery management system, which comprises the driving circuit (100, 200, 300) according to one of the preceding claims.

14. A driving method for driving coils (21 , 22, 23) of a plurality of electromagnetic switching devices, the driving method comprising controlling the switching of a power supply side switch (108, 308) for controlling power supply of the coils (21 , 22, 23) of the plurality of electromagnetic switching devices, controlling switching of each of a plurality of ground side switches (110, 310), which respectively are adapted to connect one of the coils (21 , 22, 23) of the plurality of electromagnetic switching devices to a ground potential, wherein the switching of the power supply side switch (108, 308) and the switching of the plurality of ground side switches (110, 310) is controlled to individually supply the coils (21 , 22, 23) of the plurality of electromagnetic switching devices at least with• a pick-up current for switching the respective one of the plurality of electromagnetic switching devices from an open state into a close state, or• a hold-on current for holding the respective one of the plurality of electromagnetic switching devices in the close state.

15. The driving method according to claim 14, wherein the power supply side switch (108, 308) is part of a voltage converter circuit (112), which converts an input voltage provided by a power supply into an output voltage, and wherein the driving method further comprises controlling the output voltage of the voltage converter circuit (112) by controlling switching of the power supply side switch (108, 308) such that• the coils (21 , 22, 23) of the plurality of electromagnetic switching devices are supplied with the hold-on current, when at least one of the plurality of electromagnetic switching devices is held in the closed state and when none of the plurality of electromagnetic switching devices is switched into the closed state, and• the coils (21 , 22, 23) of the plurality of electromagnetic switching devices are supplied with the pick-up current, when at least one of the plurality of electromagnetic switching devices is switched into the closed state.

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