METHOD AND CIRCUIT FOR CURRENT CONTROL

Description

[0001] The present invention relates to a method for current control with a circuit comprising a first load and / or generator component and a second load and / or generator component, between which a current can flow in a first current direction or in a second current direction, and two transistor switches connected in series between the first load and / or generator component and the second load and / or generator component, the source and emitter terminals of which are electrically short-circuited, wherein gate voltages at the gate terminals of the transistor switches are set by analog transistor controllers assigned to the transistor switches, and thus an actual current through the transistor switches is regulated.The invention further relates to a circuit for current control with a first load and / or generator component and a second load and / or generator component, between which a current can flow in a first current direction and in a second current direction, and two transistor switches connected in series between the first load and / or generator component and the second load and / or generator component, the source and emitter terminals of which are electrically short-circuited, and analog transistor regulators assigned to each of the transistor switches for setting gate voltages and thus regulating an actual current through the transistor switches.

[0002] In conventional circuits, peak currents are typically permitted. To prevent damage to devices or systems caused by these peak currents, the circuits incorporate fuses that melt above certain current levels, interrupting the circuit. Nevertheless, these high currents can still lead to issues such as EMC problems or increased circuit wear. Furthermore, in conventional systems, each blown fuse must be replaced.

[0003] Furthermore, it is often important to allow different current levels in different current directions in electrical circuits.

[0004] Publication EP 3 159 994 A describes a circuit in which two diodes with opposite polarity are arranged between a voltage source and a load. A transistor switch is connected across each diode. The control electrode of the first transistor switch receives its control signal from the output signal of the first operational amplifier, while the control electrode of the second transistor switch receives its control signal from the output signal of the second operational amplifier. The control inputs of both operational amplifiers receive the same fixed, unchanging output voltage from an internal analog power supply. This power supply is at a fixed reference potential. The positive inputs of both operational amplifiers are also at this fixed reference potential.

[0005] The operational amplifiers each tap a voltage separately across independently arranged shunts, which are connected at one end to a fixed reference potential. This results in two different voltage drops at the respective inputs of the operational amplifiers, differing in polarity and, if applicable, magnitude, depending on the associated shunt and its value. The operational amplifiers thus function as two current-measuring devices. By analogy, the first operational amplifier generates a control signal for the first transistor switch by comparing the voltage drop across the first shunt (carrying a first current) with a fixed control voltage. Simultaneously, the second operational amplifier generates a control signal for the second transistor switch by analogy, comparing the same fixed control voltage with the voltage drop across the second shunt (carrying a second current).

[0006] The Wikipedia article "Regelungstechnik" from July 19, 2021, pages 1-32, URL:https: / / de.wikipedia.org / w / index.php?title=Regelungstechnik&oldid=214014187 states that control systems can be implemented using analog or digital technology.

[0007] In publication US 7,154,253 B1, a circuit is described that uses a digital-to-analog converter (DAC) to transmit a signal to a switch for limiting a current value. The DAC receives an arbitrary digital signal and outputs it as a positive voltage to the positive input of a first operational amplifier (OPE), which then drives a transistor switch. The output signal of a second operational amplifier, which measures a voltage across a resistor, is connected to the negative input of the first operational amplifier. When the signal from the second operational amplifier reaches the level of the signal from the DAC, the first operational amplifier switches off the transistor switch, thus limiting the output current of the circuit. However, the circuit shown only allows limiting the output current in one direction.This publication also indicates that, in principle, a combination of DA or AD converters with a controller is possible in circuit technology.

[0008] Publication US 2015 / 028935 A1 describes purely analog current-limiting circuits as well as a current-limiting circuit with analog and digital components coupled by an analog-to-digital converter. In this circuit, a digital decision unit generates a control signal for a transistor, which can then switch the transistor on and off based on a digital comparison between input values ​​and maximum values ​​stored in memory devices. This allows for current limiting.

[0009] Publication WO 2020 / 165215 A1 describes an electrical switch with current regulation. For this purpose, a semiconductor switch consisting of two transistors connected in series, whose source terminals are short-circuited, is integrated between a power source and a load. A current sensor is connected in series with the semiconductor switch. The gates of the transistors are controlled by a control circuit depending on the current detected by the current sensor. The current drawn by the load can be limited by pulse-width modulation.

[0010] A method for controlling a DC circuit breaker located between a power source and an electrical load is known from publication WO 2018 / 172134 A1. The DC circuit breaker has two transistor switches connected in series, whose source terminals are short-circuited and whose gates are controlled by a control device depending on the measured values ​​of a current measuring device connected in series with the transistor switches. The control device is connected to a higher-level control system via an interface. With this method, each of the transistor switches can be switched off individually. Furthermore, with the described circuit, it is possible, for example, to set the tripping threshold of the DC circuit breaker for mains-side fault currents 25% higher than the tripping threshold for load-side fault currents.

[0011] There are currently no suitable circuits that can limit the respective current level in different current directions with minimal circuitry.

[0012] It is therefore the object of the present invention to provide a method and a simple circuit for current control with which current paths can be defined and / or short-circuit currents limited in a particularly safe and effective manner.

[0013] The problem is solved, firstly, by a current control method with a circuit comprising a first load and / or generator component and a second load and / or generator component, between which a current can flow in a first current direction or in a second current direction, and two transistor switches connected in series between the first load and / or generator component and the second load and / or generator component, whose source and emitter terminals are electrically short-circuited, wherein the gate voltages of the transistor switches are set by analog transistor controllers assigned to each transistor switch, and thus an actual current through the transistor switches is regulated, wherein the actual current is measured with a current measuring device between the transistor switches, and this measurement is then passed to the transistor controllers.wherein the actual current or the amplified actual current is passed to a first transistor controller as the first input signal of the first transistor controller and, inverted, to a second transistor controller as the first input signal of the second transistor controller, wherein a first target current for the first current direction and a second target current for the second current direction are specified to the transistor controllers by a digital controller, and wherein, depending on the respective difference between the actual current and the respective target current, corresponding gate voltages for the transistor switches are set by the transistor controllers, and thus the actual current is regulated by the transistor switches.

[0014] The method according to the invention works in its simplest form as follows: A current can flow between the first load and / or generator component and the second load and / or generator component both in a first current direction from the first to the second load and / or generator component and in a second current direction from the second to the first load and / or generator component.

[0015] The transistor switches connected in series between the first and second load and / or generator components are, assuming no fault in the circuit, in saturation, meaning they allow current to flow in both directions. Because the source and emitter terminals of the two transistor switches are short-circuited, they can, with appropriate gate control, function as switches that allow current to flow only in the first direction or only in the second. In these cases, only one of the two transistor switches is closed (i.e., in saturation), while the other is off.

[0016] The current measuring device measures the current flowing between the first and second load and / or generator components, or vice versa, which is tapped at a reference point between the transistor switches, as the respective actual current.

[0017] Preferably, the actual current is amplified by a current-sensing amplifier connected in series with the current meter. The current-sensing amplifier is then connected in series between the current-sensing device and the respective transistor regulator.

[0018] The actual current or the amplified actual current is passed to a first transistor controller as the first input signal of the first transistor controller and inverted to a second transistor controller as the first input signal of the second transistor controller.

[0019] The second input signal from the digital controller specifies a first target current in the first current direction for the first transistor regulator and a second target current in the second current direction for the second transistor regulator. The respective target current defines the maximum permissible current between the first load and / or generator component and the second load and / or generator component in the first current direction and / or in the second current direction, respectively.

[0020] Each of the two analog transistor regulators generates an output signal in the form of a gate voltage applied to the respective transistor switch. The respective output signals of the two transistor regulators depend on the difference between the actual and target current. The use of analog transistor regulators in the present invention enables a continuous and very fast real-time response to a changing actual current, which represents a significant advantage compared to the digital control of transistor switches known from the prior art, such as WO 2020 / 165215 A1 or WO 2018 / 172134 A1.

[0021] Pulse-width modulation is not used in the present invention. Instead, the inventive method achieves current limiting via linear control of the transistor switches. This means that the transistor switches are in the linear range and not pulse-width modulated during current limiting via the transistor controllers. While in publication WO 2020 / 165215 A1, current limiting is achieved via pulse-width modulation, with the energy to be transferred being limited by the pulse-width ratio, in the present invention, the energy for or during current limiting in the transistor switches is dissipated via the power loss of the transistor switches.

[0022] In the present invention, if the actual current exceeds at least a target current specified by the digital controller for one of the current directions, the transistor controllers can control the transistor switches in such a way that the respective current through the respective transistor is limited to the target current or even the respective current direction is blocked.

[0023] Because the transistor regulators operate in analog mode, such limiting or blocking can occur continuously and in real time. This protects circuit components from current spikes and thus from damage, without requiring a fuse to blow first. The current load on the circuit components can therefore be minimized over time, resulting in a high level of safety.

[0024] Preferably, the actual current is continuously transmitted to the digital controller.

[0025] In an advantageous embodiment of the method according to the invention, voltage drops across the first load and / or generator component and across the second load and / or generator component are detected and transmitted to the digital controller.

[0026] In a suitable further development of the inventive method, the controller continuously transmits the actual current and, if applicable, the voltage drops across the first load and / or generator component and across the second load and / or generator component to an external control unit via a digital coupler forming a galvanic isolation.

[0027] Preferably, if the actual current exceeds the specified target current for a predetermined period of time, the digital controller transmits a switch-off signal to at least one of the transistor controllers.

[0028] In an optional embodiment of the method according to the invention, if the actual current exceeds the respective specified target current for a predetermined period of time and the voltage drop across the load and / or generator component assigned to this target current falls below a voltage setpoint, the respective target current is set to zero by the digital controller.

[0029] In a further advantageous variant of the method according to the invention, when the circuit is switched off, the target current is reduced in a ramp- or step-like manner by the digital controller.

[0030] Furthermore, according to one embodiment of the method according to the invention, it is possible that when the circuit is switched on, the target current is increased in a ramp-like or step-like manner.

[0031] The target current set by the digital controller can be symmetrical or asymmetrical for both current directions. If each transistor regulator is given its own target current, different peak currents can be permitted depending on the current path.

[0032] The task is further accomplished by a current control circuit comprising a first load and / or generator component and a second load and / or generator component, between which a current can flow in a first current direction or in a second current direction, and two transistor switches connected in series between the first load and / or generator component and the second load and / or generator component, whose source and / orThe solution involves the following: emitter terminals are electrically short-circuited, and analog transistor controllers are assigned to each transistor switch for setting gate voltages and thus regulating an actual current through the transistor switches. A current measuring device is connected between the transistor switches to measure the actual current, and its output is connected to the respective controller inputs of the transistor controllers to transmit the measured actual current. The actual current or the amplified actual current is passed to a first transistor controller as the first input signal of the first transistor controller and, inverted, to a second transistor controller as the first input signal of the second transistor controller. The controller inputs of the transistor controllers are connected to a digital controller to specify at least one target current.

[0033] In the circuit according to the invention, the transistor switches replace electromechanical fuses and, moreover, improve their function. In principle, however, it is possible to use the circuit according to the invention as redundancy for a fuse. Conversely, at least one additional fuse can also be used in the circuit according to the invention.

[0034] Because the current measuring device for measuring the actual current is connected in series between the transistor switches in the circuit according to the invention, a simple, symmetrical circuit arrangement is obtained, which enables simple signal conditioning and simple coordination of the transistor controllers. In addition, this makes the measurement and the reaction to the measurement very fast.

[0035] By using two separate transistor regulators in the circuit according to the invention, different current limiting values ​​can be set for the respective current direction. Thus, in the present invention, it is possible, for example, to "allow" current flow in one direction only and to "prohibit" or limit it in the other direction.

[0036] In a preferred embodiment of the circuit according to the invention, a first voltage measuring device is connected in parallel to the first load and / or generator component and a second voltage measuring device is connected in parallel to the second load and / or generator component.

[0037] The transistor switches are advantageously semiconductor transistors, such as MOSFETs or IGBTs.

[0038] Preferably, the transistor controllers are either PL or PID controllers with operational amplifiers.

[0039] In an advantageous embodiment of the circuit according to the invention, the transistor regulators and the transistor switches are composed of several transistor regulator and transistor switch units connected in parallel to each other.

[0040] In a favorable embodiment of the circuit according to the invention, at least one of the transistor switches is composed of several semiconductor transistors connected in parallel to each other.

[0041] A preferred embodiment of the present invention, its structure, function and advantages are described below with reference to Figure 1 explained in more detail.

[0042] Figure 1Figure 1 shows an embodiment of a circuit 1 according to the invention. The circuit 1 comprises a first load and / or generator component 11 and a second load and / or generator component 12. In the illustrated embodiment, the first load and / or generator component 11 is a generator, but can also be, as schematically shown, a motor, at least one resistor (which can be a single resistor or composed of several resistors and can have both inductive and capacitive resistance components), and / or a battery. Furthermore, in the illustrated embodiment, the second load and / or generator component 12 is a resistor, but can also be, as schematically shown, a motor, a generator, and / or a battery.

[0043] Between the first load and / or generator component 11 and the second load and / or generator component 12, a current can flow in a first current direction 21, i.e. in the figure from A to B, as well as in a second current direction 22, i.e. in the figure from B to A.

[0044] A first transistor switch 31 and a second transistor switch 32 are connected in series between the first load and / or generator component 11 and the second load and / or generator component 12. In the illustrated embodiment, the transistor switches 31 and 32 are MOSFETs, but could also be, for example, IGBTs. In the illustrated embodiment, the transistor switches 31 and 32 have a common source terminal. If IGBTs are used for the transistor switches 31 and 32 instead of MOSFETs, their emitters are at a common electrical potential.

[0045] The common source or emitter potential of the transistor switches forms a reference potential ref for the transistor regulators 61, 62 of circuit 1, which are described in more detail below. The reference potential ref can be ground or another potential.

[0046] A current measuring device 4 is connected between the two transistor switches 31, 32, with which an actual current II ...

[0047] In the Figure 1 In the embodiment shown, a current measuring amplifier 5 is connected downstream of the current measuring device 4, with which the measured actual current IIs can be amplified and its signal reversed.

[0048] Circuit 1 comprises a first transistor controller 61 connected to a gate terminal 311 of the first transistor switch 31 and a second transistor controller 61 connected to a gate terminal 321 of the second transistor switch 32. The transistor controllers 61 and 62 are, for example, PL or PID controllers with operational amplifiers.

[0049] The measured and, if necessary, amplified actual current I Ist is passed to a controller input 611 of the first transistor controller 61, while the measured, if necessary amplified and inverted actual current -I Ist is passed to a controller input 621 of the second transistor controller 62.

[0050] Circuit 1 also includes a digital controller 7. The digital controller 7 is connected to the current-sensing amplifier 5 or, in other embodiments, directly to the current-sensing device 4. It is also connected to the controller inputs 611 and 621 of the transistor controllers 61 and 62. The actual current Iactual and the inverted actual current -Iactual are transmitted to the digital controller 7. From the digital controller 7, a setpoint current Iactual1 is transmitted as the first reference input to the controller input 611 of the first transistor controller 61 via a digital-to-analog converter (DAC) (not shown separately in circuit 1). A setpoint current Iactual2 is also transmitted as the second reference input to the controller input 621 of the second transistor controller 62 via a DAC. The respective setpoint current values ​​Iactual1 and Iactual2 correspond to the magnitude of a maximum current that is permitted to flow in current direction 21 and current direction 22, respectively, of circuit 1.The target currents Itarget1 and Itarget2 can be the same or different. In any case, however, a target current Itarget1 and Itarget2 are specified as a reference input for both transistor controllers 61 and 62, i.e., both control channels.

[0051] In circuit 1, a first voltmeter 91 is connected in parallel to the first load and / or generator component 11, and a second voltmeter 92 is connected in parallel to the second load and / or generator component 12. The first voltmeter 91 measures the voltage drop across the first load and / or generator component 11 and transmits it to the digital controller 7. The second voltmeter 92 measures the voltage drop across the second load and / or generator component 12 and transmits it to the digital controller 7.

[0052] The digital controller 7 is connected to an external control unit 8 via an interface 71, a digital coupler 72, and communication channels 73. The digital coupler 72 provides galvanic isolation between the digital controller 7 and the external control unit 8. The external control unit 8, which can also receive additional data, such as temperature readings from circuit 1, can be used, for example, to diagnose the transistor switches 31 and 32.

[0053] As exemplified in Figure 1 As shown, circuit 1 can have significantly more components or other circuit parts, such as a fuse 13 connected in series between the first load and / or generator component 11 and the second load and / or generator component 12.

[0054] Depending on the difference between the actual current Iactual and the respective target current Itarget1, Itarget2, the first transistor regulator 61 sets a gate voltage for the gate 311 of the first transistor switch 31. The second transistor regulator 62 sets a gate voltage for the gate 321 of the second transistor switch 32.

[0055] In the present invention, the transistor regulators 61, 62 function as internal regulators which, together with the respective associated transistor switches 31, 32, limit, for example, a short-circuit current in the circuit 1 (see Example 1 below). The digital controller 7 acts as an external regulator which detects the same actual current Iactual as the transistor regulators 61, 62, but—depending on the embodiment of the invention—additionally evaluates it.

[0056] Various embodiments of the method according to the invention will be described below using examples with regard to circuit 1. Figure 1 to clarify: Example 1:

[0057] If, for example, the digital controller 7 specifies a value of 100 A for both Iset1 and Iset2, and the actual current Iactual measured by the current measuring unit 4 is 200 A, both transistor regulators 61 and 62 immediately intervene and set the gate voltages of both transistor switches 31 and 32 to values ​​such that both transistor switches 31 and 32 limit the actual current Iactual to 100 A, thus preventing any current flow greater than 100 A in current directions 21 and 22. Therefore, the transistor regulators 61 and 62, together with the transistor switches 31 and 32, limit the current flowing through circuit 1 as soon as a short circuit occurs. The actual current Iactual cannot increase further. The speed of the response of circuit 1 results primarily from the fact that the transistor regulators 61, 62 as well as the transistor switches 31, 32 operate analogously and the measured actual current Iactual is continuously transmitted to the transistor regulators 61, 62. Example 2:

[0058] In a further development of the invention, the measured actual current Iactual is continuously transmitted to the digital controller 7. If the digital controller 7 detects that an energy amount resulting from the measured actual current values ​​Iactual and the corresponding time exceeds a maximum energy amount, the digital controller 7 transmits a switch-off signal to the transistor controllers 61, 62 for the transistor switches 31, 32. In this embodiment, the transistor controllers 61, 62 are not only each given a target current Itarget1, Itarget2, but indirectly, via the switch-off signal, a setpoint consisting of the target current Itarget1, Itarget2 and time. That is, the controller 7 then specifies how long the respective target current Itarget1, Itarget2 may be exceeded in the circuit 1.Only when the respective target current-time specification is exceeded do the transistor switches 31, 32 switch off by means of the transistor controllers 61, 62. Example 3:

[0059] In the example 1 above, the actual current IIs is limited in circuit 1 by means of the transistor switches 31, 32, but any short circuit that may exist in circuit 1 persists.

[0060] Therefore, in a further embodiment of the method according to the invention, the voltage drops across the first load and / or generator component 11 and across the second load and / or generator component 12 are detected by the voltage measuring devices 91, 92, and the corresponding voltages are transmitted to the digital controller 7. The digital controller 7 then evaluates, as in Example 2, the energy amount resulting from the measured actual current values ​​Iactual and the associated time, as well as the voltage drops across the load and / or generator components 11, 12, and then decides whether a short circuit or current spikes exist. Based on this, the digital controller 7 sends a switch-off signal to the transistor regulators 61, 62 for the transistor switches 31, 32, or not. Example 4:

[0061] With the circuit 1 according to the invention, or with the corresponding method, it is possible to abruptly switch off the transistor switches 31, 32 and thus the circuit 1. However, this is not desirable in some cases. Therefore, in a further embodiment of the method according to the invention, the digital controller 7 can provide signals to the transistor regulators 61, 62 for a ramp- or step-like reduction of the actual current IIs. With such a soft shutdown, the actual current IIs is gradually reduced to zero. Such a soft shutdown is possible for both current directions 21, 22. This significantly reduces the risk of damage to electronic components of the circuit 1, in particular to the transistor switches 31, 32. Example 5:

[0062] Just as a soft shutdown of circuit 1 can be performed in Example 4, circuit 1 can also be softly switched on. In such an embodiment of the invention, the digital controller 7 provides ramp- or step-shaped switch-on signals to the transistor regulators 61, 62, which convert these signals into corresponding gate voltages for the transistor switches 31, 32. This has the advantage that, particularly when circuit 1 has at least one capacitive load and / or generator component 11, 12, the transistor switches 31, 32 do not fail as quickly, and other components in the current path are also hardly stressed. Due to the ramp- or step-shaped switch-on of circuit 1, the respective capacitive load and / or generator component 11, 12 does not immediately receive the full current and can be charged gradually.If there is no short circuit, the actual current Iactual can be increased; in the event of a short circuit, the system is switched off or the actual current Iactual is reduced to a previous level. Example 6:

[0063] Since, in the present invention, each of the transistor controllers 61, 62 can be assigned its own target current I Target1 or I Target2, the flow of the actual current I Actual can only be allowed in the first current direction 21 from A to B or only in the second current direction from B to A. Example 7:

[0064] In a further embodiment of the invention, the transistor regulators 61, 62 and the transistor switches 31, 32 can each be composed of several, for example five, transistor regulator and transistor switch units connected in parallel. The current Iactual can be increased stepwise via these cascaded transistor regulator and transistor switch units, e.g., in 200 A steps up to 1 kA. Such transistor regulator and transistor switch units can be stacked or extended as needed to increase the current. Example 8:

[0065] In another embodiment of the invention it is also possible to cascade the transistor switches 31, 32 by connecting several semiconductor transistors in parallel to each other to form one of the transistor switches 31, 32.

[0066] In a further embodiment, the circuit 1 according to the invention can be remotely controlled.

[0067] Circuit 1 is independent of whether direct or alternating voltage is used.

Claims

1. Method for current control with a circuit (1) with a first load and / or generator component (11) and a second load and / or generator component (12), between which a current can flow in a first current direction (21) or in a second current direction (22), and two transistor switches (31, 32) connected in series between the first load and / or generator component (11) and the second load and / or generator component (12), wherein the source or emitter terminals (312, 322) of the transistor switches (31, 32) are electrically short-circuited, wherein gate voltages at gate terminals (311, 321) of the transistor switches (31, 32) are set by analog transistor controllers (61, 62) associated to the transistor switches (31, 32), respectively, and thus an actual current (IIst) is controlled by the transistor switches (31, 32), characterized in that the actual current (IIst) is measured with a current measuring device (4) between the transistor switches (31, 32) and said measured actual current (IIst) is forwarded to the transistor controllers (61, 62), wherein the actual current (IIst) or the actual current (IIst) as amplified value is forwarded to a first one of the transistor controllers (61) as first input signal of the first transistor controller (61) and is forwarded invertedly to a second one of the transistor controllers (62) as first input signal of the second transistor controller (62), wherein the transistor controllers (61, 62) are each given a first target current (ISoll1) for the first current direction (21) and a second target current (ISoll2) for the second current direction (22) by a digital controller (7), and the transistor controllers (61, 62) set corresponding gate voltages for the transistor switches (31, 32) depending on the respective difference between the actual current (IIst) and the respective target current (ISoll1, ISoll2), and thus the actual current (IIst) is controlled by the transistor switches (31, 32).

2. Method according to claim 1, characterized in that the actual current (IIst) is forwarded continuously to the digital controller (7).

3. Method according to claim 1, characterized in that voltage drops across the first load and / or generator component (11) and across the second load and / or generator component (12) are detected and transmitted to the digital controller (7).

4. Method according to one of the preceding claims, characterized in that the digital controller (7) continuously transmits the actual current (IIst) and, if applicable, the voltage drops across the first load and / or generator component (11) and across the second load and / or generator component (12) to an external control unit (8) via a digital coupler (72) forming a galvanic separation.

5. Method according to one of the preceding claims, characterized in that when the actual current (IIst) exceeds the respectively predetermined target current (ISoll1, ISoll2) over a predetermined period of time, a switch-off signal is transmitted by the digital controller (7) to at least one of the transistor controllers (61, 62).

6. Method according to claim 3, characterized in that when the actual current (IIst) exceeds the respectively specified target current (ISoll1, ISoll2) over a predetermined period of time and the voltage drop across the load and / or generator component (11, 12) associated to this target current (ISoll1, ISoll2) falls below a voltage target value, the respective target current (ISoll1, ISoll2) is set to zero by the digital controller (7).

7. Method according to one of the preceding claims, characterized in that when the circuit (1) is switched off, the target current (ISoll1, ISoll2) is reduced in a ramp or step manner by the digital controller (7).

8. Method according to one of the preceding claims, characterized in that when the circuit (1) is switched on, the target current (ISoll1, ISoll2) is increased in a ramp or step manner.

9. Circuit (1) for current control with a first load and / or generator component (11) and a second load and / or generator component (12), between which a current can flow in a first current direction (21) or in a second current direction (22), and two transistor switches (31, 32) connected in series between the first load and / or generator component (11) and the second load and / or generator component (12), wherein the source or emitter terminals (312, 322) of the transistor switches (31, 32) are electrically short-circuited, and analog transistor controllers (61, 62) associated to the transistor switches (31, 32) for setting gate voltages and thus controlling an actual current (IIst) through the transistor switches (31, 32), characterized in that for measuring the actual current (IIst) a current measuring device (4) is connected between the transistor switches (31, 32), wherein the output of the current measuring device (4) is connected to respective controller inputs (611, 621) of the transistor controllers (61, 62) for transmitting the respectively measured actual current (IIst), wherein the actual current (IIst) or the actual current (IIst) as amplified value is forwarded to a first one of the transistor controllers (61) as first input signal of the first transistor controller (61) and is forwarded invertedly to a second one of the transistor controllers (62) as first input signal of the second transistor controller (62), and controller inputs (611, 621) of the transistor controllers (61, 62) are connected to a digital controller (7) for specifying at least one target current (ISoll1, ISoll2).

10. Circuit according to claim 9, characterized in that the controller (7) is connected with the current measuring device (4) directly or via a current amplifier (5).

11. Circuit according to claim 9, characterized in that a first voltage measuring device (91) is connected in parallel to the first load and / or generator component (11) and a second voltage measuring device (92) is connected in parallel to the second load and / or generator component (12).

12. Circuit according to one of claims 9 to 11, characterized in that the transistor controllers (61, 62) are each PI or PID controllers with operational amplifier.

13. Circuit according to one of claims 9 to 12, characterized in that the transistor controllers (61, 62) and the transistor switches (31, 32) are composed of several transistor control units and transistor switch units connected in parallel to one another.

14. Circuit according to one of claims claim 9 to 13, characterized in that at least one of the transistor switches (31, 32) is composed of several semiconductor transistors connected in parallel to one another.