Control circuit for at least two contactors and a method for operating at least two contactors

Abstract

Control circuit (30) for at least two contactors, comprising - a first and a second terminal (11, 12) via which the control circuit (30) can be connected to the poles of an energy storage device, - at least one first output (15) and at least two second outputs (16), via which the control circuit (30) can be connected to the terminals of at least two control coils for at least two contactors, wherein the at least two second outputs (16) are each connected to the second terminal (12) via an electrical connection (8), - a holding voltage unit (10) which has an output (6) and an input (9) for receiving a control signal and which is connected via its output (6) to the at least one first output (15) and is designed to provide a holding voltage for setting a holding current for the control coils at its output (6), characterized in that the control circuit (30) has a control circuit (20) which is connected to the electrical connections (8) and the input (9) of the holding voltage unit (10) and is designed to generate a control signal dependent on the currents flowing in the electrical connections (8) and to transmit it to the holding voltage unit (10), wherein the control circuit (20) comprises a minimum current selection circuit (5) which has an output and is designed to measure the actual values ​​of the currents flowing through the electrical connections (8) and to select the minimum of the measured actual values ​​of the currents I min about their outcome, wherein the minimum current selection circuit (5) has a resistor (4) and, for each electrical connection (8), a precision rectifier (7) each having two inputs and one output, wherein each electrical connection (8) is connected to a respective input of a precision rectifier (7), while the respective other input of the respective precision rectifier (7) is fed back to the output of the respective precision rectifier (7), wherein the outputs of all precision rectifiers (7) are connected to a terminal of the resistor (4).

Description

[0001] The present invention relates to a control circuit for at least two contactors, which has a control circuit with which the currents through the control coils of the contactors are controlled. State of the art

[0002] It is becoming apparent that in the future, battery systems will increasingly be used in both stationary applications and vehicles such as hybrid and electric vehicles, and these systems will have to meet very high reliability requirements. The reason for this is that a battery failure can lead to a safety-relevant problem. In order to provide the desired performance for a particular application, a large number of battery cells are usually connected in series. This results in a high battery output voltage. Without suitable measures, this voltage is permanently present on the corresponding supply lines of the device powered by the battery and can pose a danger to maintenance personnel or users. For this reason, contactors are usually provided to electrically disconnect the battery.In motor vehicles with electric drive motors, contactors are usually installed on both the positive and negative poles of the battery. These contactors are designed for the high voltage of the battery and must be able to reliably disconnect the battery even in the event of short-circuit currents of over 1000 A.

[0003] Contactors are usually switched on and off via an electronic output stage or a control circuit that supplies power to the contactor's control coils. The control power is not negligible. However, during the switch-on process, much higher control currents are required to reliably pull in the contactors than to subsequently hold the contacts in the closed state. For this reason, it is common practice to divide contactor control into two modes: pull-in mode and hold-out mode (or pull-in or hold-out phase). The respective mode is characterized by the level of the control current, which is higher during pull-in mode than during hold-out mode. In this case, reference is made to the pull-in level and the hold-out level. Pull-in mode is only required to switch on (close) the contactors and is of relatively short duration.For the majority of their operating time, the contactors are operated in the more power-efficient hold mode. A control circuit for contactors should therefore be capable of supporting both operating modes.

[0004] DE 10 2010 041 018 A1 discloses a device for controlling a contactor, which comprises a holding current unit configured to output a holding current for the control coil of a contactor to one of its output-side outputs. With the device disclosed in DE 10 2010 041 018 A1, the control of at least one contactor during the pickup phase and the holding phase can be advantageously carried out with different voltage levels of constant voltages.

[0005] However, the components used, for example, within the device disclosed in DE 10 2010 041 018 A1, in particular the winding resistances of the contactor control coils, exhibit a temperature dependency as well as a manufacturing-related variation in their component parameters. Furthermore, the holding voltage generated by the holding current unit is set to a value determined at the time of production. The components used must therefore be designed so that the necessary holding current can be provided by the holding current unit even in extreme temperatures. However, since the conductivity of the components and thus the current flow through them, such as through the contactor's control coil, fluctuates depending on the temperature, it is necessary to dimension the components larger than would be necessary for the actually desired current.

[0006] For example, the components used in the holding circuit of the device disclosed in DE 10 2010 041 018 A1 must be dimensioned up to 66% larger for this reason, which significantly increases the necessary installation space and the costs for the components.

[0007] The document WO 01 / 01 538 A1 discloses a contactor circuit with a contactor coil, a current sensor, a switching element, a freewheeling diode and a control circuit, wherein at least one load contact can be actuated with the contactor coil, wherein the current sensor and the switching element are connected in series with the contactor coil, wherein the freewheeling diode overlaps the contactor coil and the current sensor, wherein a control command can be specified to the control circuit, on the basis of which the switching element can be actuated, wherein the control circuit is connected to the current sensor so that a contactor current flowing through the contactor coil can be regulated. Disclosure of the invention

[0008] According to the invention, a control circuit for at least two contactors is provided, which comprises a first and a second connection via which the control circuit can be connected to the poles of an energy storage device. Furthermore, the control circuit comprises at least one first output and at least two second outputs via which the control circuit can be connected to the connections of at least two control coils for at least two contactors. The at least two second outputs are each connected to the second connection via an electrical connection. Furthermore, the control circuit comprises a holding voltage unit, which has an output and an input for receiving a control signal and which is connected via its output to the at least one first output and is designed to provide a holding voltage for setting a holding current for the control coils at its output.According to the invention, the control circuit has a control circuit which is connected to the electrical connections and the input of the holding voltage unit and is designed to generate a control signal which depends on the currents flowing in the electrical connections and to transmit it to the holding voltage unit.

[0009] The control circuit comprises a minimum current selection circuit which has an output and is designed to measure the actual values ​​of the currents flowing through the electrical connections and to select the minimum of the measured actual values ​​of the currents I min about their outcome.

[0010] The minimum current selection circuit has a resistor and, for each electrical connection, a precision rectifier with two inputs and one output, wherein each electrical connection is connected to one input of a precision rectifier, while the other input of the respective precision rectifier is fed back to the output of the respective precision rectifier, wherein the outputs of all precision rectifiers are connected to one terminal of the resistor.

[0011] The advantage of such a control circuit is that the control circuit enables the holding voltage unit to be adjusted depending on the currents flowing through the contactor control coils. This allows the holding voltage provided by the holding voltage unit, or the holding current caused by the provided holding voltage, to be adjusted by control coils connected to the control circuit depending on the current flowing through the control coils themselves. This ensures that the current through the control coils can be precisely adjusted at any time. The components used to implement the control circuit then no longer need to be provisionally oversized, significantly reducing costs and the space required to implement the control circuit.

[0012] In a preferred embodiment, the holding voltage unit is designed to change the magnitude of the holding voltage provided at its output upon receipt of a control signal corresponding to this control signal. This enables, for example, linear control of the holding voltage unit or the provided holding voltage and thus of the holding current output to the first output. The type of control signal determines the type of change in the holding current.

[0013] The precision rectifiers are preferably designed as feedback operational amplifiers, with the feedback branches of the operational amplifiers each having a diode, the cathodes of the diodes each being connected to the output of their respective operational amplifier, while the anodes of the diodes are connected to the inverting input of their respective operational amplifier. Such a precision rectifier circuit also allows for a minimum current selection and, in addition, for compensating for the forward voltage of the installed diodes at room temperature, i.e., the offset of the diodes. This allows for a minimum current selection circuit implemented using precision rectifiers with diodes, which enables very precise measurement of the actual values ​​of the currents through the electrical connections.Furthermore, the operational amplifiers used here are short-circuit proof, do not require frequency compensation, have large input voltage ranges and consume little power.

[0014] In a preferred further development of one of the preceding embodiments, the control circuit comprises a first control circuit whose input is connected to the output of the minimum current selection circuit and whose output is connected to the input of the holding voltage unit. This first control circuit is preferably designed to compare a current flowing into its input with a reference value and, depending on the result of this comparison, to generate a first control signal for setting a holding voltage for the holding voltage unit and to transmit it to the holding voltage unit. This creates an external control loop within the control circuit, which operates with the returned holding current through the control coils and can be regarded as an external, superimposed current regulator.

[0015] In a preferred further development of this embodiment, the reference value corresponds to the minimum required holding current I Hmin of the contactors to be controlled. This makes it possible to control the holding voltage unit in such a way that the holding voltage provided by it or the holding currents generated by it through the control coils of the contactors connected to the control circuit always have a value that is equal to or greater than the minimum required holding current I Hmin is. I Hmin is the current that must flow through the control coils at least to keep the respective contactors in the pulled-in state during the holding phase.

[0016] In a preferred further development of this embodiment, the first control signal always corresponds to the control signal for the holding voltage unit required to set a minimum holding voltage at the output of the holding voltage unit. In this way, the second control circuit can further ensure that the control coils always supply the minimum holding current I Hminflows. With such an embodiment, disturbances that intervene in the inner control loop, for example fluctuations in the input voltage of the holding voltage unit, can also be directly compensated for on this circuit. The inner control loop reacts immediately to deviations of the holding voltage provided by the holding voltage unit from the setpoint, without this first leading to a deviation of the holding current through the control coils and thus to a disturbance that intervenes in the outer control loop. The minimum required holding voltage corresponds to the voltage at the output of the holding voltage unit that is required to cause a current to flow in each control coil of a contactor connected to the control circuit, the magnitude of which current is at least equal to the minimum required holding current I Hmin corresponds.

[0017] The control circuit preferably comprises a second control circuit which is designed to compare the first control signal generated by the first control circuit with the holding voltage provided at the output of the holding voltage unit and, depending on the result of this comparison, to superimpose a further control signal on the first control signal. This creates an inner control loop within the control circuit which operates with the holding voltage provided at the output of the holding voltage unit and can be regarded as an inner, subordinate voltage regulator. The control or input variable of the second control circuit is the first control signal generated by the first control circuit. The inner control loop therefore obtains its input values ​​from the outer control loop.

[0018] Preferably, the average duration T2 between the generation of each two consecutive further control signals by the second control circuit is smaller by a factor X than the average duration T1 between the generation of each two consecutive first control signals by the first control circuit, where 0 < X ​​< 1 applies. As a result, the time behavior of the first and second control circuits relative to one another can be determined via X, with the first control circuit always operating more slowly than the second control circuit. In other words, in such an embodiment, the inner control loop is faster than the outer control loop. Thus, a first control signal generated and transmitted by the first control circuit can always be checked by the second control circuit and corrected if necessary.

[0019] The holding voltage unit is preferably designed as a switching converter.

[0020] Furthermore, a method for operating at least two contactors is provided, which comprises at least two control coils for controlling at least two contactors and a holding voltage unit which is connected to the at least two control coils and is designed to cause a current flow through the at least two control coils by means of a holding voltage generated at its output. The method comprises the following method steps: providing a pull-in current flowing through the at least two control coils through the holding voltage unit. providing a holding current flowing through the at least two control coils through the holding voltage unit. comparing the holding currents flowing through the at least two control coils with one another and / or selecting the minimum of the holding currents flowing through the at least two control coils. comparing the minimum of the holding currents with a reference current.Generating a first control signal for the holding voltage unit for controlling the holding voltage at the output of the holding voltage unit depending on the result of the comparison between the minimum of the holding currents flowing through the at least two control coils and the reference current. Comparing the first control signal with the holding voltage present at the output of the holding voltage unit. Generating a second control signal for the holding voltage unit for controlling the holding voltage at the output of the holding voltage unit depending on the result of the comparison between the first control signal and the holding voltage present at the output of the holding voltage unit.

[0021] Preferably, the pull-in current is greater than the holding current. Advantageous developments of the invention are specified in the subclaims and described in the description. Drawings

[0022] Embodiments of the invention are explained in more detail with reference to the drawings and the following description. They show: Fig. 1 a control circuit of the prior art, Fig. 2 an embodiment of a control circuit according to the invention for two contactors, and Fig. 3 a specific embodiment of a control circuit according to the invention. Embodiments of the invention

[0023] In the Fig. Figure 1 shows a prior art control circuit 30. The control circuit 30 for controlling two contactors, of which only the control coils 50 are shown, is connected via a first and a second terminal 11, 12 to a voltage source 60, which supplies the control circuit 30 but also provides the current controlled by the control circuit 30 for controlling the contactors. The control coils 50 of the contactors are connected to the control circuit 30 via a first output 15 and two second outputs 16.The control circuit 30 has a first switch 41 and two second switches 42, wherein the first switch 41 is connected between the first pole of the voltage source 60 and the first output 15 of the control circuit 30, while the two second switches 42 are each connected between the second pole of the voltage source 60 and one of the second outputs 16 of the control circuit 30, i.e., within a respective electrical connection 8, each located between one of the outputs 16 and the second terminal 12. If the three switches 41, 42 are closed simultaneously, the control coils 50 are connected directly to the voltage source 60, and a maximum current begins to flow that is large enough to cause the contactors of the control coils 50 to attract, so that the contactors transition to the conductive state.

[0024] The control circuit 30 also has a holding voltage unit 10, which is also supplied by the voltage source 60. The holding voltage unit 10 causes the flow of a holding current, which ensures that the contactors remain closed during the holding phase following the pickup phase. Since the inertia of the electromechanical contactors does not have to be overcome, as is the case during the pickup phase, a lower current through the control coils 50 is sufficient to keep the contactors in the closed state, thus advantageously saving power. During the holding phase, the first switch 41 is therefore opened again (and, if necessary, the holding voltage unit 10 is activated), so that only the holding current flows through the control coils 50.The holding current flows through a diode 45, which is connected between the holding voltage unit 10 and the control coils 50 and has the task of preventing a current flow into the output of the holding voltage unit 10.

[0025] In addition, Fig. 1, a freewheeling diode 46 is provided, which is intended to provide a freewheeling current path for the current flowing into the control coils 50 when the holding current is switched off. The off phase is initiated by also opening the second switches 42 and, if necessary, additionally deactivating the holding voltage unit 10. Since the control coils 50 counteract any change in the currents flowing through them due to their inductance, they cause a current flow even after they are disconnected from the supply voltage, which then switches through the freewheeling diode 46 and, due to the series connection, also through the diode 45. Because the second terminals of the control coils 50 must also conduct the current, a high negative voltage is generated here, which leads to the breakdown of the Zener diodes 47 serving as clamping voltage elements.The current flow in the control coils 50 decreases rapidly, so that the magnetic field of the control coils 50 also decreases and the respective contactors drop out, thereby opening the contactors.

[0026] The first switch 41, the second switches 42 and, if applicable, the holding voltage unit 10 are controlled by a control unit 35.

[0027] In the Fig. Figure 2 shows an embodiment of a control circuit 30 according to the invention for two contactors. The control circuit 30 according to the invention has a first and a second terminal 11, 12, via which the control circuit 30 can be connected to the poles of an energy storage device, for example to the terminals of a low-voltage battery. Furthermore, the control circuit 30 according to the invention has a first output 15 and two second outputs 16, via which the control circuit 30 can be connected to the terminals of two control coils for two contactors. The first output 15 can be connected to the respective first ends or the first terminals of two control coils, while a second end of a first control coil can be connected to the first of the second outputs 16, while the second end of a second control coil can be connected to the second of the second outputs 16.The two second outputs 16 are each connected via an electrical connection 8 to the second terminal 12 of the control circuit 30. Furthermore, the control circuit 30 according to the invention has a holding voltage unit 10, which comprises an output 6 and an input 9 for receiving a control signal. The holding voltage unit 10 is connected to the first output 15 via the output 6. The holding voltage unit 10 is designed to provide a holding voltage for setting a holding current for the control coils at its output 6. In other words, the holding voltage unit 10 is designed to output a holding voltage via its output 6, which causes a current to flow through the control coils when they are connected to the control circuit 30.According to the invention, the control circuit 30 further comprises a control circuit 20, which is connected on the input side to the electrical connections 8 and on the output side to the input 9 of the holding voltage unit 10. In other words, the control circuit 20 is connected via one of its inputs to one of the electrical connections 8 of the control circuit 30 and is connected via its output to the input 9 of the holding voltage unit 10. The control circuit 20 is designed to generate a control signal dependent on the currents flowing in the electrical connections 8 and thus, if connected to the control circuit 30, the currents flowing in the control coils, and to transmit this control signal to the holding voltage unit 10. In other words, the control circuit 20 is designed to generate a control signal dependent on the currents through the electrical connections 8 and to supply it to the holding voltage unit 10 via the input 9.The properties, i.e. for example the amplitude of a control signal generated by the control circuit 20, are therefore dependent on the currents through the electrical connections 8.

[0028] The control circuit 30 according to the invention is not limited to controlling just two contactors. Control circuits 30 according to the invention can also be implemented for controlling additional contactors, for example, 4, 8, or n contactors, which can therefore be connected to more than two control coils.

[0029] Fig. 3 shows a special embodiment of a control circuit 30 according to the invention. This essentially shows a control circuit 30 according to Fig. 1, which is a Fig. 2, but further developed control circuit 20. The descriptions of the components apart from this control circuit 20 or the facts and relationships relating to them can be found in the descriptions of the Fig. 1 and Fig. 2 or the Fig. 1 and Fig. 2 itself. The components with the same designation in Fig. 3 correspond to those of the first embodiment of the Fig. 2 and those from the example of a control circuit 30 of the prior art in the Fig. 1, so that what is said there regarding these components also applies to the second embodiment of the Fig. 3 is to be transmitted. In this exemplary embodiment, the control circuit 30 is connected to two control coils 50 via its first and second outputs 15, 16, while it is connected to an energy storage device 60 designed as a voltage source via its first and second terminals 11, 12. Neither the control coils 50 nor the energy storage device 60 are to be considered part of the control circuit 30.

[0030] In the Fig.3, the control circuit 30 according to the invention comprises a control circuit 20, which in turn comprises a minimum current selection circuit 5 and a first and second actuating circuit 1, 2. In this embodiment, the minimum current selection circuit 5 comprises a shunt resistor for each electrical connection 8, with a shunt resistor being located within each of the electrical connections 8, between the switching means 42 of the respective electrical connection 8 and the terminal 12 of the control circuit 30. The minimum current selection circuit 5 is connected by its inputs to the measuring terminals of the shunt resistors, with the inputs of the minimum current selection circuit 5 being identical to the inputs of a precision rectifier 7 for each electrical connection 8.In other words, the minimum current selection circuit 5 has a precision rectifier 7 for each electrical connection 8, wherein each input of a precision rectifier 7 is connected to a respective electrical connection 8 via a respective measuring connection of a shunt resistor. Furthermore, the precision rectifiers 7 each have a second input and an output, wherein the respective second input is fed back to the output of the respective precision rectifier 7. The minimum current selection circuit 5 further has a resistor 4, wherein the outputs of all precision rectifiers 7 are connected to the first connection of this resistor 4. This means that each precision rectifier 7 within the minimum current selection circuit 5 is connected via its respective output to the same connection of the resistor 4.

[0031] In this exemplary embodiment, the precision rectifiers 7 are designed as feedback operational amplifiers, wherein the inverting input of the operational amplifiers is fed back to the output of the respective operational amplifier. Within the feedback branches or the feedback of the operational amplifiers, a diode 3 is arranged in each case, the anode of which is connected to the respective inverting input of the respective operational amplifier or to the connection of the resistor 4, while the cathodes of the diodes 3 are each connected to the output of their respective operational amplifier. The other connection of the resistor 4, to which the precision rectifiers 7 are not connected, is connected to the output of the minimum current selection circuit 5, via which the minimum current selection circuit 5 is connected to the input of the first control circuit 1.The minimum current selection circuit 5 is designed to measure the actual values ​​of the currents flowing through the electrical connections 8, in this embodiment, via the shunt resistors and to determine the minimum of the measured actual values ​​of the currents I. minvia the output of the minimum current selection circuit 5. In this exemplary embodiment, the minimum current selection is implemented via the diodes 3 within the precision rectifiers 7. At any given time, the lowest of the input values ​​at the inputs of the precision rectifiers 7 is output via the output of the minimum current selection circuit 5. Both the use of shunt resistors for measuring the actual values ​​of the currents and the use of precision rectifiers 7 are optional for the implementation of a minimum current selection circuit 5 of a control circuit 30 according to the invention. The design of the precision rectifiers 7 as an operational amplifier with diodes 3 is also chosen purely as an example in this exemplary embodiment.Control circuits 30 according to the invention can also be implemented with differently designed minimum current selection circuits 5, for example using only diodes 3, wherein the measurement of the actual values ​​of the currents through the electrical connections 8 can also be carried out in a manner other than via shunt resistors.

[0032] The minimum current selection circuit 5 transmits the minimum of the measured actual values ​​of the currents I min to the first control circuit 1, whose output is connected to the input 9 of the holding voltage unit 10. In this embodiment, the first control circuit 1 is designed to receive the minimum of the measured actual values ​​of the currents I transmitted to it via its input. minwith a reference value, which in this embodiment is provided purely by way of example by a reference transmitter 13. In other words, the first control circuit 1 in this embodiment is designed to compare a current fed back to its input with a reference value. In this embodiment, the reference value is the minimum required holding current I Hmin of the contactors to be controlled, i.e., the current that must at least flow through the control coils 50 of the contactors so that they can keep the contactor in the holding state, i.e., in the closed state during the holding phase. Furthermore, the first control circuit 1 is designed to generate a current which is dependent on the result of the comparison between the minimum of the measured actual values ​​of the currents I min with the minimum required holding current I Hmindependent first control signal for setting a holding voltage for the holding voltage unit 10 and transmitting it to the holding voltage unit 10 via its input 9. The properties of the first control signal generated by the first control circuit 1 correspond to the result of the comparison. For example, in this exemplary embodiment, the magnitude of the first control signal is greater, the stronger the minimum of the measured actual values ​​of the currents I min of the minimum required holding current I Hmin The first control circuit 1 is therefore designed in this embodiment to generate a signal which, among other things, depends in amount and duration on the result of the comparison between the minimum of the measured actual values ​​of the currents I min and a reference value, which in this embodiment corresponds to the minimum necessary holding current I Hminthe contactor corresponds, and to supply it to the holding voltage unit 10. The holding voltage unit 10 is designed in this exemplary embodiment to change the amount of the holding voltage provided by it at its output 6 and thus the amount of the holding current flowing into the first output 15 upon receipt of a first control signal corresponding to this first control signal. In this exemplary embodiment, the holding voltage unit 10 is designed purely by way of example as a switching converter and the first control signal corresponds to a duty cycle which determines the degree of control of the switching converter. In this exemplary embodiment, the holding current is therefore regulated purely by way of example via a change in the holding voltage at the output of the holding voltage unit 10, corresponding to the received first control signal.Furthermore, the control circuit 30 has a second control circuit 2, which is designed to compare the first control signal generated by the first control circuit 1 with the holding voltage provided by the holding voltage unit 10 at the output 6 thereof and, depending on the result of this comparison, to superimpose a further control signal on the first control signal. In other words, the first control signal generated by the first control circuit 1 can be corrected via the second control circuit 2 by superimposing a correction signal. The first control signal, which in this exemplary embodiment is compared with the holding voltage provided by the holding voltage unit 10, corresponds purely by way of example to a control signal for the holding voltage unit 10 required to set a minimum required holding voltage at the output 6 of the holding voltage unit 10.In other words, the first control signal always corresponds to the signal that must be applied to the input 9 of the holding voltage unit 10 so that it provides the minimum necessary holding voltage at its output 6. The minimum necessary holding voltage is the voltage that must at least be present at the output 6 of the holding voltage unit 10 so that a current flow through the control coils 50 of all contactors results, which current is sufficient to keep each contactor in the pulled-in state during the holding phase. In this exemplary embodiment, the average duration T2, which lies between the generation of two consecutive further control signals by the second actuating circuit 2, is a factor X smaller than the average duration T1, which lies between the generation of two consecutive first control signals by the first actuating circuit 1, where 0 < X ​​< 1.In other words, the first control circuit 1 operates slower than the second control circuit 2, whereby the second control circuit 2 is always able to correct the control signal generated by the first control circuit 1.

[0033] Through the interaction of minimum current selection circuit 5, first control circuit 1, and second control circuit 2, a two-loop or cascaded control system is realized within control circuit 30, through which the currents through electrical connections 8 and thus also through control coils 50 can be set to an optimal value, particularly during the contactor holding phase. First control circuit 1 closes an outer control loop, which uses the holding current through the control coils 50 connected to control circuit 30 as the controlled variable, while second control circuit 2 closes an inner control loop, which uses the holding voltage provided by holding voltage unit 10 as the controlled variable.

[0034] However, both the first and the second control circuits 1, 2 are optional for a control circuit 30 according to the invention. Control circuits 30 according to the invention can also be implemented with control circuits 20 without these components, with which, for example, a minimum current through the electrical connections 8 can still be set or regulated. In this exemplary embodiment, both the first and the second control circuits 1, 2 operate continuously, i.e., they continuously compare their input variables with their respective reference values ​​and continuously generate and transmit control signals depending on the result of this comparison.

Claims

[1] Control circuit (30) for at least two contactors, comprising - a first and a second terminal (11, 12) via which the control circuit (30) can be connected to the poles of an energy storage device, - at least one first output (15) and at least two second outputs (16), via which the control circuit (30) can be connected to the terminals of at least two control coils for at least two contactors, wherein the at least two second outputs (16) are each connected to the second terminal (12) via an electrical connection (8), - a holding voltage unit (10) which has an output (6) and an input (9) for receiving a control signal and which is connected via its output (6) to the at least one first output (15) and is designed to provide a holding voltage for setting a holding current for the control coils at its output (6), characterized by , that the control circuit (30) has a control circuit (20) which is connected to the electrical connections (8) and the input (9) of the holding voltage unit (10) and is designed to generate a control signal dependent on the currents flowing in the electrical connections (8) and to transmit it to the holding voltage unit (10), wherein the control circuit (20) comprises a minimum current selection circuit (5) which has an output and is designed to measure the actual values ​​of the currents flowing through the electrical connections (8) and to select the minimum of the measured actual values ​​of the currents I min about their outcome, wherein the minimum current selection circuit (5) has a resistor (4) and, for each electrical connection (8), a precision rectifier (7) each having two inputs and one output, wherein each electrical connection (8) is connected to a respective input of a precision rectifier (7), while the respective other input of the respective precision rectifier (7) is fed back to the output of the respective precision rectifier (7), wherein the outputs of all precision rectifiers (7) are connected to a terminal of the resistor (4). [2] Control circuit (30) according to claim 1, wherein the holding voltage unit (10) is designed to change the amount of the holding voltage provided at its output (6) upon receipt of a control signal corresponding to this control signal. [3] Control circuit (30) according to claim 1, wherein the precision rectifiers (7) are designed as feedback operational amplifiers, wherein the feedback branches of the operational amplifiers each have a diode (3), wherein the cathodes of the diodes are each connected to the output of their respective operational amplifier, while the anodes of the diodes (3) are connected to the inverting input of their respective operational amplifier. [4] Control circuit (30) according to one of claims 1 to 3, wherein the control circuit (20) comprises a first control circuit (1), the input of which is connected to the output of the minimum current selection circuit (5) and the output of which is connected to the input (9) of the holding voltage unit (10), wherein the first control circuit (1) is designed to compare a current flowing into its input with a reference value and, depending on the result of this comparison, to generate a first control signal for setting a holding voltage for the holding voltage unit (10) and to transmit it to the holding voltage unit (10). [5] Control circuit (30) according to claim 4, wherein the reference value corresponds to the minimum necessary holding current I Hmin corresponds to the contactor to be controlled. [6] Control circuit (30) according to claim 4 or 5, wherein the first control signal always corresponds to the control signal for the holding voltage unit (10) necessary for setting a minimum necessary holding voltage at the output (6) of the holding voltage unit (10). [7] Control circuit (30) according to one of claims 4 to 6, wherein the control circuit (20) comprises a second control circuit (2) which is designed to compare the first control signal generated by the first control circuit (1) with the holding voltage provided at the output (6) of the holding voltage unit (10) and, depending on the result of this comparison, to superimpose a further control signal on the first control signal. [8] Control circuit (30) according to claim 7, wherein the average duration T2, which lies between the generation of two successive further control signals by the second control circuit (2), is smaller by a factor X than the average duration T1, which lies between the generation of two successive first control signals by the first control circuit (1), where 0 < X ​​< 1. [9] Method for operating at least two contactors of a control circuit (30) according to one of claims 1 to 8, comprising - at least two control coils to control at least two contactors, - a holding voltage unit (10) which is connected to the at least two control coils and is designed to cause a current flow through the at least two control coils by means of a holding voltage generated at its output, the method comprising the following method steps: -providing a starting current (S1) flowing through the at least two control coils by the holding voltage unit (10); -providing a holding current (S2) flowing through the at least two control coils by the holding voltage unit (10); - comparing the holding currents (S3) flowing through the at least two control coils with each other and / or selecting the minimum of the holding currents flowing through the at least two control coils; - comparing the minimum of the holding currents with a reference current (S4); - generating a first control signal (S5) for the holding voltage unit (10) for controlling the holding voltage at the output of the holding voltage unit (10) depending on the result of the comparison between the minimum of the holding currents flowing through the at least two control coils and the reference current; - comparing the first control signal (S6) with the holding voltage present at the output of the holding voltage unit (10); - generating a second control signal (S7) for the holding voltage unit (10) for controlling the holding voltage at the output of the holding voltage unit (10) depending on the result of the comparison between the first control signal and the holding voltage present at the output of the holding voltage unit (10).

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