Circuit arrangement, electrical energy storage with such a circuit and use of the same as energy storage

Description

[0001] The present invention relates to a circuit arrangement with at least one supercapacitor and at least one bypass circuit, an electrical energy storage device with a circuit arrangement and the use of a circuit arrangement as an energy storage device.

[0002] Energy can be stored through chemical conversion (e.g. in accumulators) or through physical processes (e.g. in capacitors).

[0003] Capacitors can be differentiated by their construction. For example, there are ceramic capacitors, plastic film capacitors, metal-paper capacitors, and electrolytic capacitors. These capacitor types typically have a capacitance in the range of picofarads (pF) to approximately 1 farad.

[0004] Supercapacitors are a special type of capacitor. Supercapacitors can have a capacitance in the range of kilofarads or more. The capacitance of supercapacitors results from two different technical effects and can therefore be divided into double-layer capacitance and pseudocapacitance. While double-layer capacitance is based on charge separation, pseudocapacitance is the result of redox reactions. During operation, the double-layer capacitance and pseudocapacitance add up to the total capacitance of the supercapacitor.

[0005] A special feature of supercapacitors is their low nominal voltage, typically 2.7 V, compared to conventional capacitors. At the same time, supercapacitors are extremely sensitive to higher voltages. Even a slight excess of the nominal voltage during charging can lead to permanent damage to the supercapacitor. Therefore, when supercapacitors are integrated into electronic circuits, it is advisable to protect them from higher voltages.

[0006] Since a voltage higher than 2.7 V is desired in many applications, supercapacitors are often connected in series, which adds up the nominal voltages. However, due to the series connection, the individual supercapacitors can charge at different rates during the charging process. This is primarily due to manufacturing tolerances, which can cause nominally identical supercapacitors to actually have different capacitances. The resulting different charging behavior can cause individual supercapacitors to exceed their nominal voltage and become permanently damaged.

[0007] To prevent damage to series-connected supercapacitors, WO 2018 / 237320 A1 proposes a balancing circuit in which each supercapacitor is assigned a bypass circuit. The bypass circuits are connected to a bus system and, when activated, effect charge equalization between the series-connected supercapacitors. Activation is achieved via a clock generator. The circuit is complex due to the use of a bus system and the clock generator. Furthermore, the clock generator only effects periodic, not permanent, charge equalization. Thus, the capacitors are only temporarily protected.

[0008] EP 1 274 105 B1 also proposes a bypass circuit for supercapacitors. The bypass circuit comprises a transistor, a low-pass filter, and a detector unit that generates a logic signal that is supplied to a charging device for charging the supercapacitor, thereby controlling the charging current used to charge the supercapacitor. Due to the detector unit and the control of the charging device, this bypass circuit is also very complex.

[0009] DE 600 23 772 T2 discloses a circuit arrangement comprising a double-layer capacitor and a shunt regulator connected in parallel with the double-layer capacitor, as well as an NPN transistor connected in parallel with the double-layer capacitor. One terminal of the shunt regulator is connected to the base of the NPN transistor.

[0010] US 2020 / 0044459 A1 discloses a device and a method for protecting the batteries of a battery pack from overcharging.

[0011] It was therefore an object of the invention to provide a circuit arrangement that offers better and cost-effective protection for supercapacitors against exceeding the nominal voltage.

[0012] This object is achieved by a circuit arrangement according to claim 1.

[0013] The circuit arrangement according to the invention comprises at least one supercapacitor and at least one bypass circuit connected in parallel with the supercapacitor. The at least one bypass circuit comprises at least two bypass transistors operating as switching elements, each connected in parallel with the supercapacitor, and a cross-regulator connected in parallel with the supercapacitor, the switching threshold of which defines the switching point for the bypass transistor.

[0014] The invention uses a cross-regulator to trigger the protective function – the overvoltage protection – for the supercapacitor. A cross-regulator can generally be understood as a component that is connected in parallel with the supercapacitor and, at least in the active state, always draws enough current to keep the voltage across the supercapacitor constant. In the bypass circuit, the cross-regulator acts as a threshold switch. A threshold switch is generally an electronic or electrical component that combines the function of a sensor with a switching function. The switching process is triggered when the physical quantity "measured" by the sensor exceeds a preset limit (the threshold). In this case, the measured quantity is a quantity of the circuit arrangement, namely the capacitor voltage applied to the supercapacitor.The cross regulator is preferably switchable and has a control input for this purpose. A Zener diode (non-switchable), also called a Z-diode, or a TL431 (switchable), can be used as a cross regulator. The cross regulator can therefore also be referred to as a parallel regulator, shunt regulator, Zener diode, or threshold switch.

[0015] The switching threshold is an intrinsic value of the cross-regulator. If the cross-regulator has a control input, the switching threshold must be reached at the control input for the cross-regulator to switch. For a TL431, the switching threshold is 1.5 V to 2.5 V; for a Zener diode, the breakdown voltage corresponds to the switching threshold.

[0016] During the charging process, the supercapacitor is first charged as usual with a charging current. The bypass circuit remains in a passive state as long as the switching threshold of the cross-regulator is not reached. When the switching threshold is reached, the at least two bypass transistors are controlled by the cross-regulator. The bypass circuit is then in an active state. In this state, the bypass circuit conducts current around the supercapacitor. This current does not further charge the supercapacitor, thus preventing an overvoltage and protecting the supercapacitor.

[0017] The amplification effect of transistors is not binary, but follows a characteristic curve and depends on the voltage across the capacitor (base-emitter voltage) and / or a control signal. A higher base-emitter voltage increases the amplification, meaning the transistor is "driven on" further. With a lower control signal, the amplification effect of a transistor is lower. Simple capacitors have higher nominal voltages than supercapacitors. These higher voltages are then also available to drive transistors in a bypass circuit. As a result of the higher voltages, the transistors in the bypass circuit conduct more strongly and immediately conduct a higher current around the capacitor, thus protecting it very effectively. With simple capacitors, bypass circuits therefore achieve a sufficient bypass effect.

[0018] This is not necessarily the case with supercapacitors due to their low nominal voltage. It has been shown that the low nominal voltage of supercapacitors results in the control signal not switching the transistors optimally, thus resulting in only reduced current conduction, meaning the supercapacitors are not optimally protected.

[0019] By arranging at least two bypass circuits in parallel with the supercapacitor, more current can be directed around the supercapacitor. The bypass circuits are independent of each other. Different switching points can therefore be provided for each controlled bypass transistor. This allows the supercapacitor's protection to be switched on in multiple stages, for example, depending on the applied voltage.

[0020] A further improvement in the protection effect is achieved by having each bypass circuit comprise two bypass transistors, each connected in parallel with the supercapacitor, acting as switching elements. The switching threshold of the cross-regulator defines the switching point for the two bypass transistors connected in parallel. The bypass transistors are preferably nominally identical. In this case, the two bypass transistors are connected together, allowing a higher current to be bypassed around the supercapacitor.

[0021] As described, supercapacitors are subject to manufacturing tolerances. If several supercapacitors are connected in series in a circuit, the individual supercapacitors charge at different rates. This effect increases with the difference in the actual capacitance of the individual capacitors. The inventors have recognized that this effect can be reduced by connecting several capacitors in parallel, thereby better protecting the individual supercapacitors. Advantageous developments therefore provide at least two supercapacitors connected in parallel, which together form a supercapacitor group. In other words, several supercapacitors are connected in parallel, and in parallel with them are provided the two bypass circuits or a single bypass circuit with two bypass transistors.Connecting multiple capacitors in parallel statistically reduces the likelihood of significant deviations from the nominal capacity of the supercapacitor group. It is particularly preferable for the supercapacitors connected in parallel to be nominally identical. Identical components have the same tolerance limits, making the statistical effect particularly effective.

[0022] Preferably, several supercapacitors or supercapacitor groups are connected in series, with each of the several supercapacitors or each of the several supercapacitor groups being assigned at least one parallel-connected bypass circuit as described above. As a result, the circuit arrangement has a higher total nominal voltage, resulting in more application possibilities for the circuit arrangement.

[0023] The bypass transistor is preferably a bipolar transistor. A MOSFET (metal oxide semiconductor field-effect transistor) can also be used. In any case, it is preferred that the bypass transistor delivers a sufficiently high current, especially > 2 A, between the base and emitter even at low voltages, especially < 2.7 V. In this way, the bypass transistor provides good protection for the supercapacitor.

[0024] The capacitor voltage applied to the supercapacitor or supercapacitor group at which the cross-regulator switches, i.e., reaches its switching threshold, is preferably defined by a voltage divider connected in parallel with the supercapacitor, the node of which is connected to the control input of the cross-regulator of the at least one bypass circuit. In this way, the bypass circuit can be adapted to the supercapacitor or supercapacitor group. The voltage divider preferably comprises at least two series-connected resistors, between which the node lies and which influence the node potential. Particularly preferably, the voltage dividers of the two bypass circuits connected in parallel to the same supercapacitor, and thus their node potentials, are different. In this way, the two bypass circuits are connected in cascade at different times, namely at different capacitor voltages.This gradually reduces the charging current as it approaches the nominal voltage of the supercapacitor(s), thus reducing the risk of the charging voltage "overshooting".

[0025] The voltage divider of the at least one bypass circuit preferably comprises a variable resistor arrangement, by means of which the node potential can be selected. In other words, the variable resistor arrangement can be used to select the capacitor voltage at which the cross-regulator reaches its switching threshold. In this way, different bypass circuits, for example, within a bypass cascade or for different supercapacitors, can be implemented with the same components, thereby reducing production costs. The node potential is then influenced depending on the desired switching point or the capacitance of the parallel-connected supercapacitor.

[0026] The variable resistance arrangement preferably has several parallel sub-strands, each with a different electrical resistance, and comprises a selection means, wherein the selection means can be used to select precisely one sub-strand as the conductive sub-strand, or several sub-strands can be selected as conductive sub-strands. The selection means makes it easy to select the exact sub-strand(s) that are(are) correct for the supercapacitor to be used. The selection can be made by fixed contact, for example, by soldering, or by variable contact, for example, by means of a changeover switch.

[0027] If two bypass circuits are used for a supercapacitor or supercapacitor group, and their cross-regulators are to switch at different capacitor voltages, a first sub-phase can be selected in one bypass circuit and a second sub-phase in the other bypass circuit if identical components are used. This means that the node potentials of the two voltage dividers are always different, and consequently, the switching times of the cross-regulators also differ. This makes it easy to implement different switching times for the two bypass circuits.

[0028] As an alternative to a plurality of sub-strings, the variable resistance arrangement preferably includes a potentiometer. A potentiometer enables continuous adjustment of the resistance and thus ultimately the switching point. A circuit arrangement with a potentiometer can thus be more flexibly adapted to specific requirements.

[0029] The at least one bypass circuit preferably comprises an evaluation transistor for controlling an evaluation unit, wherein the switching threshold of the cross-regulator defines the switching point for the evaluation transistor. The evaluation transistor makes it possible to determine, by means of an evaluation unit, whether the cross-regulator has switched and the bypass circuit is active. An output of the evaluation transistor is connected to a control input of the evaluation unit. The circuit arrangement can also comprise the evaluation unit. Preferably, a common or central evaluation unit is provided for several bypass circuits of the circuit arrangement. If, for example, different switching times are defined for the bypass transistors in two bypass circuits connected in parallel, the evaluation unit can be used to determine which of the two bypass circuits is switched on and when.This demonstrates another advantage of the different node potentials with multiple bypasses. Multiple evaluation transistors allow for more precise (step-by-step) monitoring of the state of the circuit / supercapacitor, for example, to determine proper charging to the desired capacitor voltage, or to detect aging or other defects. Therefore, a central evaluation unit is particularly preferably provided in a circuit arrangement with at least two bypass circuits, with an output of each evaluation transistor of the at least two bypass circuits being connected to an input of the evaluation unit.

[0030] It may be desirable to interrupt the charging process. This is the case, for example, when all supercapacitors in the circuit arrangement are fully charged. This state can be determined, as described, using the evaluation transistors and the evaluation unit. The circuit arrangement preferably comprises a switching element configured to open and close the connection between a terminal for a power source and the supercapacitor. The switching element is preferably a relay.

[0031] Preferably, a resistor is connected in series with the bypass transistor, and the resistor and the bypass transistor are connected together in parallel with the supercapacitor. This prevents a short circuit from occurring if the bypass circuit is activated.

[0032] The cross regulator preferably defines the switching point for the bypass transistor by connecting an output of the cross regulator to a control input of each bypass transistor. A resistor is particularly preferably arranged between the output (anode terminal) of the cross regulator and the input of each bypass transistor. The use of a resistor between the cross regulator and the bypass transistor serves to compensate for tolerances. The resistors ensure that the actual switching times of the bypass transistors, which always vary due to tolerances, are not too far apart.

[0033] It has been shown that it can be useful to protect supercapacitors even during discharging. In particular, a discharge below a predetermined value is fundamentally undesirable. The circuit arrangement therefore preferably comprises undervoltage protection. The undervoltage protection preferably comprises a control unit, in particular a microcontroller. The control unit is configured to detect the capacitor voltage, determine an impending undervoltage based on a predetermined limit value, and then interrupt the discharge process. Particularly preferably, the control unit is connected to a switching element, wherein the switching element is located between the load and the supercapacitor. The control unit is configured to control the switching element when the capacitor voltage falls below the predetermined limit value.

[0034] According to one embodiment of the invention, one and the same switching element, arranged between a common connection of the power source and load and the supercapacitor, is sufficient to disconnect the capacitor in the event of both undervoltage and overvoltage. In other embodiments, two switching elements can also be provided. In this case, one switching element is located between the power source and the supercapacitor, and the other switching element is located between the load and the supercapacitor. The switching elements can then be controlled by the control unit when a limit value for the undervoltage or overvoltage is reached. Alternatively, a switching relay can be used, with which the supercapacitor can be connected selectively to the power source or the load.

[0035] As mentioned, the power source and the load can be directly connected to each other, with the circuitry then being connected to a common terminal at the power source and the load. Such a connection is conceivable, for example, in a photovoltaic system (power source) to which an electric vehicle with a local energy storage device (load) is connected. The circuitry then stores any excess energy and releases it when the load requires more than the photovoltaic system supplies.

[0036] In addition to the switching device, in both cases a (high-performance) rectifier and / or diodes can be used at the connection between the circuit arrangement and the power source or the circuit arrangement and the load. If the power source and load can be connected to the circuit arrangement separately, a diode is preferably arranged between the power source and the supercapacitor and / or a diode between the load and the supercapacitor, with the diodes each allowing only the desired current direction, i.e., from the power source to the supercapacitor and from the supercapacitor to the load. Diodes and / or (high-performance) rectifiers can also be used in parallel with the switching device.If, for example, electric motors are directly powered by the stored energy from the circuit arrangement, the use of a "hard" switching device, such as a relay, is problematic: When the switching device is switched on, a high current flows suddenly, which is disadvantageous. To mitigate this, a diode or a high-performance rectifier can be connected in parallel with the switching device to initially allow only a lower current flow, with the electric motor then only receiving the maximum possible current flow when the switching device is switched on. Such a configuration is particularly conceivable if the circuit arrangement is used as an intermediate storage device, for example between a fuel cell and electric motors in a vehicle drive. A diode or high-performance rectifier connected in parallelA parallel-connected (high-performance) rectifier can optionally be connected in series with another switching device in order to prevent any current flow to the consumer.

[0037] If several supercapacitors or supercapacitor groups are connected in series, the capacitor voltage can be measured across the entire supercapacitor group, whereby a safety margin in addition to the sum of the nominal voltages of the individual supercapacitors must be taken into account in the specified undervoltage limit. However, the control unit is preferably configured to measure the capacitor voltage at each supercapacitor or supercapacitor group and compare it with the limit. The connection to the load is disconnected if one of the supercapacitors or one of the supercapacitor groups falls below the limit.

[0038] The object of the invention is also achieved by an electrical energy storage device with a housing and a circuit arrangement arranged in the housing as described above. The housing protects the circuit arrangement and in particular the supercapacitors from external influences. This allows the circuit arrangement to be set up, for example, in a private area and connected to a photovoltaic system and charged by it. The circuit arrangement can also be used in a vehicle, in particular as an intermediate storage device in vehicles with alternative drives, e.g. in electric vehicles and in vehicles powered by hydrogen, natural gas, or LPG. For example, the circuit arrangement can be used in a fuel cell vehicle as an intermediate storage device between the fuel cell and drive motors or as a primary energy source for an electric vehicle (EV).The circuit arrangement can also be used as a buffer in a charging station for electric vehicles. Another possible application concerns wind turbines. Currently, wind turbines are switched off (taken out of the wind) when there is sufficient energy in the power grid. During this time, they are prevented from feeding energy into the grid, which reduces their efficiency. The circuit arrangement can be used here as a buffer, which is charged whenever the power grid cannot absorb energy. When the power grid is ready to absorb energy again, the energy stored in the buffer can be fed into the grid. The circuit arrangement can also be used as a mobile storage device. For example, it can be arranged on a (Euro) pallet and loaded into a vehicle (e.g., a van). The vehicle can then be used mobile to charge other vehicles (broken-down electric vehicles, e-scooters, etc.).The circuit arrangement can also be used as a mobile storage device in an electric vehicle, where it represents the primary source but is replaceable. A corresponding use of the circuit arrangement is therefore also the subject of the invention. Due to the high potential charging and discharging currents of supercapacitors, their use can shorten the charging times of electric vehicles without having to increase the line capacitance to the charging stations, particularly if the charging station or charger is equipped with the circuit arrangement according to the invention, which benefits this application. The capacitors can then be charged over a longer period of time during which no consumer is connected.

[0039] The invention is illustrated and explained below by way of example with reference to the figures. Figure 1 shows a circuit diagram of a circuit arrangement according to a first embodiment, Figure 2 shows a circuit diagram of a circuit arrangement according to a second embodiment, and Figure 3 shows a circuit diagram of a circuit arrangement according to a third embodiment.

[0040] The Figure 1 The circuit arrangement 1 shown comprises a supercapacitor 3 and an anode terminal 5 and a cathode terminal 7, to which a power source (not shown) and a load (not shown) can be connected. When a power source is connected, the supercapacitors 3 are charged.

[0041] Two bypass circuits 9, 9' are provided in parallel with each of the supercapacitors 3. The bypass circuits 9, 9' are identical in terms of the components used, which is why only one is described in detail below.

[0042] The bypass circuit 9, 9' comprises a plurality of strings, each connected in parallel with the supercapacitor 3: two bypass strings 15, a regulator string 25, and a voltage divider string. The strings are explained in more detail below: The bypass string 15 comprises the load path of a bypass transistor 17, wherein the load path is connected in series with a first resistor 19. The bypass circuit 9, 9' comprises two bypass strings 15, each with a bypass transistor 17. The bypass strings 15 are each connected in parallel with the supercapacitor 3. The bypass transistor 17 is a pnp bipolar transistor.

[0043] The regulator train 25 comprises the load path of a cross regulator 27, which is connected in series with a second resistor 29. The cross regulator 27 is a TL431. It is a controllable cross regulator 27 with three terminals: an anode terminal 32, a cathode terminal 31, and a reference terminal 33. The load path runs between the anode terminal 32 and the cathode terminal 31.

[0044] Between the cross regulator 27 and the second resistor 29 is a node 35, which is connected to the base of both bypass transistors 17. A third resistor 37 is arranged between each node 35 and the base for tolerance compensation. If a voltage below the switching threshold is present between the reference terminal 33 and the anode of the cross regulator 27, the cross regulator 27 is blocked. The base of both bypass transistors 17 is then at the anode potential. If the switching threshold of the cross regulator 27 is reached at its reference terminal 33, the cross regulator 27 conducts, and the system voltage drops across the second resistor 29. The base of the bypass transistors 17 is therefore pulled to the potential of the cathode, causing the bypass transistors 17 to become conductive. In this way, the switching threshold of the cross regulator 27 defines the switching point for the bypass transistors 17.After the bypass transistors 17 are switched on, a portion of the charging current flows past the supercapacitor 3 through the bypass transistor 17 and thus no longer charges the supercapacitor 3. The supercapacitor 3 is thus protected from overvoltage.

[0045] The voltage divider string includes a voltage divider 41. The voltage divider 41 includes a single fourth resistor 43 connected in series with a variable resistor array 45. A node 47 is arranged between the fourth resistor 43 and the variable resistor array 45, which is connected to the reference terminal 33, i.e., the control input, of the cross-regulator 27. The voltage divider 41 thus defines the capacitor voltage at which the cross-regulator 27 reaches its switching threshold and switches.

[0046] The variable resistor arrangement 45 comprises several parallel-connected sub-strings, each with a resistor 55, 57, 59 and a selection means 61. The resistors 55, 57, 59 are of different sizes. Using the selection means 61, exactly one sub-string can be selected as the conductive sub-string. In this way, the voltage divider 41 can be adapted to the respective supercapacitor 3 to be protected. The selection of the conductive sub-string influences the capacitor voltage at which the cross-regulator 27 reaches its switching threshold, since the node potential at node 47 changes depending on which sub-string is selected as the conductive sub-string.

[0047] The two bypass circuits 9, 9', which are connected in parallel to the same supercapacitor 3, have, as mentioned, the same components, which are interconnected in the same way. However, the variable resistor arrangements 45 of the two bypass circuits 9, 9' are set differently. In the embodiment shown, the first sub-phase with resistor 55 is selected as the conductive sub-phase in one bypass circuit 9, and the second sub-phase with resistor 57 is selected as the conductive sub-phase in the second bypass circuit 9'. As a result, the cross regulators 27 of the bypass circuits 9 reach their switching threshold at different capacitor voltages and control their respective bypass transistors 17 at different times.

[0048] The circuit arrangement 1 further comprises an evaluation line 71, which includes an evaluation transistor 73 for controlling an evaluation unit (not shown) and is connected on the one hand to the anode terminal 5 and on the other hand to an evaluation output 75. The evaluation transistor 73 is also controlled by the cross-regulator 27 as soon as it reaches its switching threshold. In this way, the switching threshold of the cross-regulator 27 defines the switching point for the evaluation transistor 73. The evaluation unit can be connected to the evaluation output 75. In this way, the evaluation unit can be used to determine whether the respective bypass circuit 9, 9' is active or passive.

[0049] The circuit arrangement 1 according to Figure 2has, for example, four series-connected supercapacitor groups 81, each with, for example, two parallel-connected supercapacitors 3. Each supercapacitor group 81 is protected from overvoltage by two bypass circuits 9, 9', which are connected in parallel to the associated supercapacitor group 81. The bypass circuits 9, 9' are identical to those of the embodiment according to Figure 1 and shown here only schematically.

[0050] In the embodiment shown, all supercapacitors 3 are nominally identical. This reduces the likelihood of significant deviations of the supercapacitor groups 81 from their nominal capacity, which in this case corresponds to twice the nominal capacity of an individual supercapacitor 3.

[0051] By connecting the supercapacitor groups 81 in series, the nominal voltages of the individual supercapacitors 3 add up to a total nominal voltage of the circuit arrangement 1. In this embodiment, a single supercapacitor 3 has a nominal voltage of 2.7 V; the circuit arrangement 1 therefore has a total nominal voltage of 4 • 2.7 V = 10.8 V.

[0052] In other embodiments, the number of supercapacitors 3 or supercapacitor groups 81 connected in series may be different. Likewise, in other embodiments, the supercapacitor groups 81 may comprise more than two supercapacitors 3 connected in parallel.

[0053] The Figure 3 The circuit arrangement 1 shown comprises a supercapacitor 3 which is protected from overvoltage by a bypass circuit 9.

[0054] The circuit arrangement 1 further comprises a relay 91, by means of which the supercapacitor 3 is connected to a load (not shown) and a power source (not shown). The load and the power source are thus located before the relay 91, and the supercapacitor 3 is located after the relay 91. A microcontroller 93 detects the voltage before and after the relay 91. Furthermore, the microcontroller 93 is connected to the bypass circuit 9 and receives the signal from the evaluation transistor 73 as an input signal. In the case of several supercapacitors 3 connected in series, the microcontroller 93 detects, on the one hand, the total voltage across all supercapacitors 3 and, by means of the evaluation transistors 73, the voltage present across the individual supercapacitors 3 (or supercapacitor groups 81).

[0055] If the microcontroller 93 detects that the voltage behind the relay 91 exceeds a predetermined upper limit, i.e. an overvoltage is imminent, or falls below a predetermined lower limit, i.e. an undervoltage is imminent, it opens the relay 91 via a control line 95 and thus protects the supercapacitor 3.

[0056] Since the microcontroller 93 also detects the voltage before the relay 91, it can detect the voltage state on the consumer and power source side even when the relay 91 is open and, depending on this, close the relay 91 again when the respective limit value is again exceeded or undershot, or otherwise leave it open. List of reference symbols

[0057] 1Circuit arrangement 3Supercapacitor 5Anode connection 7Cathode connection 9, 9'Bypass circuit 15Bypass strand 17Bypass transistor 19first resistor 25Regulator string 27Cross regulator 29Second resistor 31Cathode connection 32Anode connection 33Reference connection 35Node 37Third resistor 41Voltage divider 43Fourth resistor 45Variable resistor arrangement 47Node 55Resistor 57Resistor 59Resistor 61Selection device 71Evaluation strand 73Evaluation transistor 75Evaluation output 81Supercapacitor group 91Relay 93Microcontroller 95Control line

Claims

1. Circuit arrangement (1) having at least one supercapacitor (3) and at least one bypass circuit (9, 9') connected in parallel with the supercapacitor (3), wherein the at least one bypass circuit (9, 9') comprises at least two bypass transistors (17) which operate as switching elements and are each connected in parallel with the supercapacitor (3), characterised in that the at least one bypass circuit (9, 9') comprises a cross-regulator (27) connected in parallel with the supercapacitor (3), the switching threshold of which defines the switching point for the at least two bypass transistors (17) connected in parallel.

2. Circuit arrangement (1) according to claim 1, characterised in that at least two supercapacitors (3) connected in parallel are provided, which together form a supercapacitor group (81) and in that the supercapacitors (3) connected in parallel are nominally identical in construction.

3. Circuit arrangement (1) according to one of the preceding claims, characterised in that a plurality of supercapacitors (3) or a plurality of supercapacitor groups (81) are connected in series, wherein at least one bypass circuit (9, 9') connected in parallel according to one of the preceding claims is associated with each of the plurality of supercapacitors (3) or each of the plurality of supercapacitor groups (81).

4. Circuit arrangement (1) according to one of the preceding claims, characterised in that the bypass transistor (17) of the at least one bypass circuit (9, 9') is a bipolar junction transistor or a MOSFET.

5. Circuit arrangement (1) according to one of the preceding claims, characterised in that the at least one bypass circuit (9, 9') comprises a voltage divider (41) which is connected in parallel with the supercapacitor (3) and whose node (47) is connected to a control input of the cross-regulator (27) of the at least one bypass circuit (9, 9'), wherein the voltage divider (41) defines the capacitor voltage at which the cross-regulator (27) reaches its switching threshold when applied to the supercapacitor (3).

6. Circuit arrangement (1) according to one of the preceding claims, characterised in that at least two bypass circuits (9, 9') connected in parallel to the supercapacitor (3) or to the supercapacitor group (81) are provided.

7. Circuit arrangement (1) according to claim 5 and claim 6, characterised in that the voltage dividers (41) of the two bypass circuits (9, 9') connected in parallel to the same supercapacitor (3) are different.

8. Circuit arrangement (1) according to claim 5 or 7, characterised in that the voltage divider (41) of the at least one bypass circuit (9, 9') comprises a variable resistor arrangement (45) by means of which the node potential can be selected.

9. Circuit arrangement (1) according to claim 8, characterised in that the variable resistor arrangement (45) has a plurality of parallel partial strings each with a different electrical resistance (55, 57, 59) and comprises a selection means (61), wherein it is possible to select precisely one partial string as a conductive partial string by means of the selection means (61) or wherein it is possible to select a plurality of partial strings as conductive partial strings, or in that the variable resistor arrangement (45) comprises a potentiometer.

10. Circuit arrangement (1) according to one of the preceding claims, characterised in that the at least one bypass circuit (9, 9') comprises an evaluation transistor (73) for activating an evaluation unit, wherein the switching threshold of the cross-regulator (27) defines the switching point for the evaluation transistor (73).

11. Circuit arrangement (1) according to claim 10 with at least two bypass circuits (9, 9'), characterised by a central evaluation unit, wherein an output of each evaluation transistor (73) of the at least two bypass circuits (9, 9') is connected to an input of the evaluation unit.

12. Circuit arrangement (1) according to one of the preceding claims, characterised in that a first resistor (19) is connected in series with the bypass transistor (17) and in that the first resistor (19) and the bypass transistor (17) are connected together in parallel with the supercapacitor (3).

13. Circuit arrangement (1) according to one of the preceding claims, characterised in that an output of the cross-regulator (27) is connected to a control input of each bypass transistor (17), a third resistor (37) being arranged between the output of the cross-regulator (27) and the input of each bypass transistor (17).

14. Electrical energy storage device with a housing and a circuit arrangement (1) arranged in the housing according to one of the preceding claims.

15. Use of a circuit arrangement (1) according to one of claims 1 to 13 as an energy storage device in a photovoltaic system, in a vehicle with alternative drive, in a charging station for electric vehicles, in a buffer storage of a wind power plant or in a mobile storage system.