Circuit arrangement

Abstract

A circuit arrangement (10) comprises a supercapacitor (12) and, connected in parallel to the supercapacitor (12), a bypass circuit (30) that prevents or limits charging of the supercapacitor (12) when activated. The arrangement is also provided with a switch (100) that is controlled by a control unit (110) and by means of which the bypass circuit (30) can be transferred to the activated state.

Description

[0001] CIRCUIT ARRANGEMENT

[0002] DESCRIPTION

[0003] The present invention relates to a circuit arrangement, an electrical energy storage device, the use of a circuit arrangement as an energy storage device and a method for operating a circuit arrangement.

[0004] Energy can be stored through chemical conversion (e.g. in accumulators) or through physical processes (e.g. in capacitors).

[0005] 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.

[0006] 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.

[0007] A special feature of supercapacitors is their low nominal voltage, typically 2.4 to 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.

[0008] 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.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] US 2020 / 0044459 A1 discloses a device and a method for protecting the batteries of a battery pack from overcharging.

[0013] It has been shown that the known circuit arrangements for supercapacitors are inadequate and that even with these circuits, deviations can occur when charging the supercapacitors.

[0014] The object of the invention was therefore to improve the protection of supercapacitors during the charging process. This object is achieved by the circuit arrangement according to the invention.

[0015] The circuit arrangement comprises at least one supercapacitor and a bypass circuit connected in parallel with the supercapacitor, which, in an active state, prevents or limits charging of the supercapacitor. The bypass circuit is in an inactive state below a predefined voltage threshold of a capacitor voltage applied to the supercapacitor and is switched to the active state when the predefined voltage threshold is exceeded. The circuit arrangement is characterized in that the bypass circuit comprises a switch controllable by a control unit, by means of which the bypass circuit can be switched to the active state, in particular from the inactive state to the active state, independently of the predefined voltage threshold.

[0016] If the bypass circuit is already in the active state due to exceeding the predefined voltage threshold, strictly speaking, it will not be switched to the active state by (additionally) switching the switch. Even in this case, however, the switch is still capable of switching the bypass circuit from the inactive state to the active state.

[0017] The bypass circuit is designed to protect the supercapacitor from overvoltage. When the bypass circuit is activated, it preferentially conducts current around the supercapacitor. This current does not further charge the supercapacitor, preventing an overvoltage and protecting the supercapacitor. If no external voltage is applied to the circuit, i.e., no power source is connected to the supercapacitor, the bypass circuit, in its active state, discharges the supercapacitor. In any case, electrical energy is converted into heat by a bypass circuit in the active state and is "lost," i.e., dissipated into the environment.

[0018] The charging and discharging of supercapacitors, triggered by manufacturing tolerances and varying degradation, does not always proceed in a completely identical manner. If supercapacitors connected in series are always fully charged, these problems are barely noticeable. However, it has been recognized that over time, increasingly large deviations between the charge states of several series-connected supercapacitors arise if the supercapacitors are repeatedly incompletely charged and discharged. The invention therefore creates a way to switch the bypass circuit to the active state independently of the predefined voltage threshold, thus compensating for deviations. The switch has an open and a closed state. In the closed state, the switch conducts current; in the open state, the switch does not conduct current.Preferably, the bypass circuit is switched to the active state when the switch is closed. The switch is preferably a transistor, with the switch being in the closed state when the transistor is switched on. Alternatively, other switches can also be used.

[0019] In advantageous further developments, several supercapacitors are connected in series, with a bypass circuit connected in parallel to each supercapacitor as mentioned above, and each switch of the bypass circuits being controllable independently of the other switches. In this way, the switches of all bypass circuits can be opened or closed as needed, and the bypass circuits can be switched to the active state as needed.

[0020] Supercapacitors are divided into three different capacitor families depending on the design of their electrodes:

[0021] Double-layer capacitors have carbon electrodes or their derivatives with a very high static double-layer capacitance. The Faradaic pseudocapacitance accounts for only a small proportion of the total capacitance.

[0022] Pseudocapacitors have electrodes made of metal oxides or conductive polymers and have a very high proportion of Faradaic pseudocapacitance.

[0023] Hybrid capacitors have asymmetrical electrodes, one with a high double-layer capacitance and the second with a high pseudocapacitance.

[0024] The supercapacitors of the circuit arrangement according to the invention are particularly preferably lithium titanate oxide supercapacitors (LTO supercapacitors). LTO supercapacitors are hybrid capacitors. In LTO supercapacitors, the negative graphite electrode is replaced by a sintered electrode made of a titanium spinel (Li4Ti50i2). The lithium titanate electrode has a significantly larger effective surface area than a graphite electrode, a factor of 30. For this reason, very high charging and discharging currents in the range greater than 10C can be achieved. Thus, the power density is approximately 1,200–3,500 W / kg (2,700–7,500 W / liter). The high charging and discharging currents can lead to the deviations mentioned above during incomplete charging cycles. Therefore, the circuit arrangement according to the invention is particularly advantageous when using LTO supercapacitors.

[0025] In advantageous further developments, the control unit is connected to the supercapacitors in such a way that it can detect the capacitor voltage applied to the respective supercapacitor and / or the capacitor potential applied to a positive terminal of the respective supercapacitor. The capacitor voltage or the capacitor potential provide information about the magnitude of the deviation in the state of charge of several supercapacitors. In this way, the control unit can determine which bypass circuit should be set to the active state. Preferably, the positive terminal of each supercapacitor is connected to its own input of the control unit, whereby the control unit receives an input signal in the form of a potential depending on the actually existing capacitor potential. By comparing the potentials, the control unit can determine the capacitor voltage of the respective capacitor and from this determine the deviations in the state of charge.Alternatively, the capacitor voltage can be measured directly by a measuring unit and transmitted as information to the control unit. The measuring unit is connected to the supercapacitor and the control unit.

[0026] With supercapacitors connected in series, the capacitor potential increases with each additional supercapacitor. It is desirable to protect the control unit inputs from excessively high potentials. Therefore, a protective circuit with a voltage divider is preferably arranged between each positive pole and the corresponding control unit input. The voltage divider is connected to the positive pole at one end and has two series-connected resistors with a node between them, and the control unit input is connected to the node. As a result, the potential at the control unit input is lower than the capacitor potential of the respective supercapacitor. The other end of the voltage divider is preferably at a zero potential (UBO) of the circuit arrangement. This zero potential does not have to correspond to ground potential.

[0027] A connection of the control unit is preferably also at the zero potential of the circuit arrangement.

[0028] As already mentioned, the potential increases along the length of the series-connected supercapacitors. It is therefore advantageous if the resistors are matched to the nominally maximum capacitor potential of the corresponding supercapacitor. The nominally maximum capacitor potential is determined by the nominal voltages of the series-connected supercapacitors and the position of the respective supercapacitor in the series circuit, starting from the cathode. For example, if three supercapacitors with a nominal voltage of 2.7 V are connected in series, the nominally maximum capacitor potential, starting from the anode, is 2.7 V for the first supercapacitor, 5.4 V for the second supercapacitor, and 8.1 V for the third supercapacitor.

[0029] It is particularly advantageous if the resistors of the voltage divider are selected such that the potential present at the input of the control unit is below a predetermined value, which is preferably 5 V. The predetermined value is particularly preferably identical for all inputs. In other words, the voltage dividers of the bypass circuits of adjacent supercapacitors are preferably different. The resistors of each voltage divider are, in particular, selected such that the predetermined value is not exceeded at the nominally maximum capacitor potential of the associated supercapacitor.

[0030] The voltage threshold is preferably defined by the bypass circuit itself, especially by its electronic components. It is therefore not specified, influenced, or even controlled from outside the bypass circuit.

[0031] In advantageous developments, the bypass circuit has at least one bypass transistor connected in parallel with the supercapacitor, which operates as a switching element, and a cross-regulator connected in parallel with the supercapacitor. When its switching threshold is reached, the bypass transistor switches on (becomes conductive) and thereby puts the bypass circuit into the active state, in which the bypass circuit conducts current around 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 TL431 (switchable), for example, can be used as a cross-regulator. The cross-regulator can therefore also be referred to as a parallel regulator, shunt regulator, or threshold switch.

[0032] 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.

[0033] 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 collector and emitter even at low voltages, especially < 2.7 V. In this way, the bypass transistor provides good protection for the supercapacitor. The switching threshold is an intrinsic variable 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.

[0034] During the charging process, the supercapacitor is first charged as usual by a charging current. The bypass circuit remains in a passive (inactive) state as long as the switching threshold of the cross-regulator is not reached. When the switching threshold is reached, at least one bypass transistor is 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, so that an overvoltage does not occur, at least if the charging current of the supercapacitor is less than or equal to the current conducted around the supercapacitor by the bypass circuit. In any case, the amount of current charging the supercapacitor is reduced by the bypass circuit in the active state, thus protecting the supercapacitor.

[0035] 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 and limit the maximum current of the base terminal. The resistors ensure that the actual switching times of the bypass transistors, which always vary due to tolerances, are not too far apart.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] A further improvement in the protection effect can be achieved if each bypass circuit comprises 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.

[0040] The bypass circuit preferably further comprises a display transistor connected in parallel with the supercapacitor. The display transistor is also controlled by the cross-regulator as soon as it reaches its switching threshold. In this way, the switching threshold of the cross-regulator defines the switching point for the display transistor. A light-emitting diode and a resistor are also connected in series in the load path of the display transistor. A resistor is arranged between the regulator node and the base of the display transistor to compensate for tolerances and to limit the maximum current of the base terminal. The display transistor can differ from the bypass transistor due to the further connection to the light-emitting diode. The resistance between the regulator node and the base of the display transistor is preferably selected such that the display transistor switches at the same time as the bypass transistors.When the cross regulator reaches its switching threshold, it switches the indicator transistor, whereupon the LED lights up, indicating that the bypass circuit is in its active state.

[0041] The bypass circuit preferably comprises a voltage divider connected in parallel with the supercapacitor, the voltage divider node of which is connected to a control input of the cross-regulator. The voltage divider defines that the cross-regulator reaches its switching threshold when the predefined voltage threshold is reached on the supercapacitor. The voltage divider preferably has two series-connected resistors, between which the voltage divider node is arranged. Alternatively, at least one of the two resistors can be formed by 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, for different supercapacitors, can be implemented using the same components, thus reducing production costs. The node potential is then influenced depending on the desired switching point or the capacitance of the parallel-connected supercapacitor.

[0042] 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.If two bypass circuits are used for a supercapacitor 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.

[0043] 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.

[0044] As described, the switch has an open and a closed state, and preferably switches the bypass transistor on when closed. The switch and the cross-regulator are particularly preferably connected in parallel and can switch the bypass transistor on independently of each other. If the cross-regulator has already switched the bypass transistor on, operating the switch has no effect. The switch is nevertheless suitable for switching the bypass transistor on regardless of the voltage threshold.

[0045] The bypass circuit preferably comprises an optocoupler with a transmitting side and a receiving side, the transmitting side being connected to the control unit and the receiving side forming the switch. The transmitting side and the receiving side of an optocoupler can communicate with each other, i.e., in particular, transmit signals, but are galvanically isolated from each other. Due to the different potentials of the various supercapacitors, it is advantageous to provide a component with galvanic isolation between the control unit and the switch. Other components that provide galvanic isolation, such as an isolating transformer or a relay, can also be used instead of the optocoupler.

[0046] The transmitting side of the optocoupler preferably has an LED, and the receiving side a phototransistor. The LED is controlled by the control unit of the circuit arrangement. For this purpose, the LED is connected to an output of the control unit. If the LED is activated by the control unit ("HIGH level triggering"), it switches the phototransistor on, causing the switch to conduct, i.e., to close. If the LED is deactivated, the switch opens. In other words, the switch can be switched between the open and closed states depending on a signal from the transmitting side.

[0047] The control unit preferably comprises at least one multiplexer, in particular a 74HC4067. Particularly preferably, the control unit comprises a multiplexer that forms the inputs for the input signals and a multiplexer that forms the outputs for the switches. The multiplexers are preferably connected to a central control element of the control unit, for example, an Arduino Nano.

[0048] In advantageous further developments, several control units are provided, wherein each control unit is connected to at least one switch of a bypass circuit and wherein neighboring control units are connected to one another with galvanic isolation. The control units can communicate with one another through their connection and, in particular, exchange information on the charge states, i.e., the capacitor voltages, of individual supercapacitors assigned to them. In this way, several assemblies are created, each consisting of a control unit and several associated supercapacitors, each with an associated bypass circuit. Depending on the area of ​​application, such assemblies can be interconnected in various ways, i.e., in particular, in series and / or parallel. In this way, an energy storage device is provided that is precisely tailored to the desired application.

[0049] The electrically isolated connection of the control units is achieved, in particular, by an optical connection, for example, a fiber optic cable. Particularly preferably, each control unit is assigned several switches, whereby the control unit can control the switches assigned to it independently of one another. In advantageous further developments, each control unit is connected to its own display of the circuit arrangement. In particular, the input signals of the control unit, the capacitor voltages of the supercapacitors associated with the control unit, the active bypass circuits, the states of all bypass circuits, and / or other information can be visualized or displayed as numerical values ​​on the display.

[0050] The circuit arrangement can comprise one or more dedicated temperature sensors connected to the control unit. In particular, each supercapacitor and / or each bypass circuit is assigned a temperature sensor. The control unit can activate the bypass circuit(s) depending on the signal from the temperature sensors.

[0051] 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 the bypass circuit is provided in parallel.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. The above description regarding series-connected supercapacitors also applies to series-connected supercapacitor groups.

[0052] 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 by the control unit based on the input signals, as described. The circuit arrangement preferably comprises a switching element connected to the control unit, which is configured to open and close the connection between a terminal for a power source and the supercapacitor. The switching element is preferably a relay connected in series with the supercapacitors.

[0053] The object of the invention is also achieved by an electrical energy storage device comprising a housing and at least one circuit arrangement arranged in the housing as described above. The series-connected supercapacitors offer a higher nominal voltage than is possible with a single supercapacitor. At the same time, deviations in the charge states of the supercapacitors are avoided by the circuit arrangement according to the invention.

[0054] Particularly preferably, several circuit arrangements are connected in series, each comprising several supercapacitors connected in series. The energy storage device then advantageously provides the zero potential for the first circuit arrangement in the series, for example, through a connection to ground. All subsequent circuit arrangements have the higher final potential of the preceding circuit arrangement in the series as their zero potential. In an energy storage device with a nominal voltage of, for example, 75 V and three identical circuit arrangements, the zero potential of the first circuit arrangement is 0 V, the zero potential of the second circuit arrangement is 25 V, and the zero potential of the third circuit arrangement is 50 V.

[0055] At least one temperature sensor can be arranged in the housing to measure the temperature within the housing. The temperature sensor is connected to the control unit.

[0056] The housing is preferably earthed.

[0057] The energy storage device preferably comprises at least one display connected to the control unit, in particular galvanically isolated, on which, for example, the temperature in the housing, the input signals of the control units, the capacitor voltages of the supercapacitors, the active bypass circuits, the states of all bypass circuits associated with the control unit, and / or further information are displayed.

[0058] Optionally, the energy storage device can include a communications unit connected to the control unit. The communications unit serves as a data logger and for communication with other devices. The communications unit preferably has at least one wireless or wired interface, for example, Wi-Fi. Remote maintenance is also possible in this way. The communications unit is preferably galvanically isolated from the control unit.

[0059] The object of the invention is also achieved by the use of a circuit arrangement according to the above description 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 device of a wind turbine or in a mobile storage device. In particular in a photovoltaic system, incomplete charging processes regularly occur in winter, which, without the circuit arrangement according to the invention, would lead to deviations in the charge states of series-connected supercapacitors over time. These deviations are avoided by the invention. It can also happen that the programming of the inverter of the photovoltaic system switches off before the supercapacitors reach the voltage threshold.In this case, the supercapacitors are never fully charged to the point where the voltage threshold is reached and the bypass circuits are switched to the active state. Therefore, even with a supposedly full charge, charge balancing through the bypass circuits does not automatically occur. The circuit arrangement according to the invention is particularly advantageous in such cases, as it can ensure charge balancing even below the voltage threshold.

[0060] The object of the invention is also achieved by a method for operating a circuit arrangement according to the above description. In the method, the control unit controls the switch of the bypass circuit such that the bypass circuit is switched to the active state regardless of the predefined voltage threshold.

[0061] The control unit preferably controls the switches of several bypass circuits depending on the potentials applied to the control unit's inputs. As described above, the potentials provide information about the capacitor voltage applied to each supercapacitor and are therefore particularly suitable as a starting point for controlling the switches.

[0062] The control unit preferably compares the potentials of several bypass circuits present at the control unit's inputs with each other, controls the switches of selected bypass circuits based on the comparison, and thereby sets the selected bypass circuits to the active state. Advantageously, the control unit first converts the potentials of several bypass circuits present at the control unit's inputs into comparison values ​​using a factor specified by the respective voltage divider, then compares the comparison values ​​of the bypass circuits with each other, controls the switches of selected bypass circuits based on the comparison, and thereby sets the selected bypass circuits to the active state. The values ​​and arrangement of the resistors of the voltage divider are known.It is therefore possible to convert a potential applied to a specific input of the control unit into the capacitor potential, which was previously reduced by the voltage divider. The capacitor voltage is then calculated as the difference between the capacitor potentials of two adjacent supercapacitors. This allows the capacitor voltages of each supercapacitor to be determined as a reference value and subsequently compared with each other. Particularly preferred is the comparison to determine which supercapacitor has the highest charge (capacitor voltage), and only the bypass circuit associated with that supercapacitor is activated. In this way, only the charging process of a single supercapacitor is halted, allowing all other supercapacitors to "catch up." As a result, comparatively little electrical energy is lost as heat.If two or more supercapacitors have the same capacitor voltage, the bypass circuit of the first supercapacitor starting from the anode is preferably put into the active state.

[0063] Alternatively, the comparison can be used to determine which supercapacitors have a higher capacitor voltage than at least one other supercapacitor in the same series, and the bypass circuits of the supercapacitors with higher capacitor voltages are then switched to the active state. In this case, all but one supercapacitor would no longer be charged.

[0064] Whether a bypass circuit is activated can depend on one or more conditions. For example, a bypass circuit can be activated as soon as its associated supercapacitor has a higher capacitor voltage than at least one other supercapacitor in the same series. Alternatively, the bypass circuit can only be activated when there is a certain difference in the capacitor voltages and / or a difference to a certain number of supercapacitors in the same series. The difference is preferably less than 10% of the nominal voltage and / or between 0.02 V and 0.2 V.

[0065] Within the scope of the method according to the invention, it is also possible to define a (higher) differential limit for the capacitor voltages at which the control unit detects a fault and, for example, triggers an output in the form of an alarm signal, such as a red LED or an acoustic warning signal. Automatic, wireless transmission of a message (e.g., email, SMS, or push notification) to a predefined recipient (e.g., service technicians, owners, etc.) is also possible. A large difference between two or more supercapacitors can sometimes no longer be compensated by the bypass circuits. In such cases, the control unit can also initiate an emergency shutdown, for example, using the relay, which stops the charging of all supercapacitors.

[0066] The invention is illustrated and explained below by way of example with reference to the figures.

[0067] Figure 1 shows a circuit diagram of a circuit arrangement. Figure 2 shows a circuit diagram of an electrical energy storage device.

[0068] The circuit arrangement 10 shown in Figure 1 comprises two supercapacitors 12, which can be connected to a power source (not shown) and / or a load (not shown) via an anode terminal 14 and a cathode terminal 16. When a power source is connected, the supercapacitors 12 are charged; when a load is connected, the supercapacitors 12 are discharged. Due to tolerances, charging and discharging are not entirely identical, so that over time, and especially with repeated, incomplete charging and discharging, deviations between the charge states of the two supercapacitors 12 may occur.

[0069] Each supercapacitor 12 has a positive pole 17 and a negative pole 18. The potential at the positive pole 17 is higher and is also referred to as the capacitor potential. The voltage applied to one of the supercapacitors 12, i.e., the potential difference between the positive pole 17 and the negative pole 18, is referred to as the respective capacitor voltage. The supercapacitors 12 are each designed for a nominal voltage. In the embodiment shown, this nominal voltage is 2.7 V. The nominal voltage is reached when the respective supercapacitor is fully charged. Due to the series connection, starting from the cathode connection 16, the first supercapacitor 12 has a maximum capacitor potential of 2.7 V at its positive pole 17. The subsequent, second supercapacitor 12, in contrast, has a maximum capacitor potential of 2 * 2.7 V = 5.4 V at its positive pole 17.

[0070] A bypass circuit 30 is connected in parallel with the supercapacitor 12. The bypass circuit 30 comprises a plurality of strings, each connected in parallel with the supercapacitor 12: two bypass strings 40, a display string 50, a regulator string 60, and a voltage divider string 70. The strings are explained in more detail below.

[0071] The bypass lines 40 are identical in construction and are each connected in parallel with the supercapacitor 12. Therefore, only one bypass line 40 is described. The bypass line 40 comprises the load path of a bypass transistor 42, which is connected in series with a first resistor 44. The bypass transistor 42 is a PNP bipolar transistor.

[0072] The regulator strand 60 comprises the load path of a cross regulator 62, wherein the load path is connected in series with a second resistor 64. The cross regulator 62 is a TL431. It is a controllable cross regulator 62 with three terminals: an anode terminal, a cathode terminal, and a reference terminal. The load path runs between the anode terminal and the cathode terminal. The cathode terminal of the cross regulator 62 is connected to the negative pole 18 of the supercapacitor 12. Between the anode terminal of the cross regulator 62 and the second resistor 64 is a regulator node 63, which is connected to the base of both bypass transistors 42. A third resistor 46 is arranged between the regulator node 63 and the base for tolerance compensation. If a voltage below the switching threshold is present between the reference terminal and the anode terminal of the cross regulator 62, the cross regulator 62 is blocked.The base and emitter of both bypass transistors 42 are then both at the potential of the positive pole 17. Thus, no current flows along the base-emitter path, so the bypass transistors are not switched on. If a current source is applied to the anode terminal 14 and the cathode terminal 16, the supercapacitor 12 is charged. Below a voltage threshold of the capacitor voltage applied to the supercapacitor 12, predefined by the switching threshold of the cross-regulator 62, the bypass circuit 30 is thus in an inactive state.

[0073] The voltage divider string 70 has a voltage divider 72. The voltage divider 72 comprises two series-connected resistors, a fifth resistor 73 and a sixth resistor 74. A voltage divider node 75 is arranged between the fifth resistor 73 and the sixth resistor 74, which is connected to the reference terminal, i.e., the control input of the cross-regulator 62. The ratio of the resistors 73, 74 defines the capacitor voltage at which the cross-regulator 62 reaches its switching threshold and switches.

[0074] If the switching threshold of the cross regulator 62 is reached at its reference terminal, the cross regulator 62 conducts, and the system voltage drops across the second resistor 64. The base of the bypass transistors 42 is therefore pulled to the potential of the negative pole, causing the bypass transistors 42 to be switched on, i.e., conductive. This places the bypass circuit 30 in the active state. In this way, the switching threshold of the cross regulator 62 defines the switching point for the bypass transistors 42. After the bypass transistors 42 are switched on, a portion of the charging current flows past the supercapacitor 12 through the bypass transistor 42, thus no longer charging the supercapacitor 12. In this way, the supercapacitor 12 is protected from overvoltage at least when the current flowing from the power source to the supercapacitor 12 does not exceed the current conducted around the supercapacitor 12 by the bypass circuit 30.

[0075] The circuit arrangement 10 further comprises a display branch 50, which comprises a display transistor 52. The display transistor 52 is also controlled by the cross regulator 62 as soon as it reaches its switching threshold. In this way, the switching threshold of the cross regulator 62 defines the switching point for the display transistor 52. A third resistor 46 is again arranged between the regulator node 63 and the base of the display transistor 52 for tolerance compensation. Furthermore, a light-emitting diode 54 and a fourth resistor 56 are connected in series in the load path of the display transistor 52. When the cross regulator 62 reaches its switching threshold, it switches the display transistor 52, whereupon the light-emitting diode 54 lights up, thus indicating that the bypass circuit 30 is in its active state.

[0076] In the embodiment shown here, the bypass transistors 42 and the display transistor 52 are nominally identical (similar in construction), just as the third resistors 46 are nominally identical. As a result, the transistors 42, 52 all switch at approximately the same time. The bypass transistors 42 and the display transistor 52 may be different in other embodiments. Preferably, the third resistors 46 are in any case adapted to the respective transistors 42, 52 such that the transistors 42, 52 all switch at approximately the same time.

[0077] The circuit arrangement 10 further comprises an optocoupler 90, which has a transmitting side 92 with a light-emitting diode 94 and a receiving side 96 with a phototransistor 98 as a switch 100. The transmitting side 92 and the receiving side 96 are galvanically isolated from one another. The light-emitting diode 94 is controlled by a control unit 110 of the circuit arrangement 10. For this purpose, the light-emitting diode 94 is connected on the one hand to an output 114 of the control unit 110 and on the other hand to a zero potential UBO of the circuit arrangement 10. The switch 100 is connected in parallel with the cross-regulator 62.

[0078] The control unit 110 is also connected to the zero potential UBO of the circuit arrangement 10.

[0079] The circuit arrangement 10 comprises a display 116 connected to the control unit 110, on which information about the supercapacitors 12, for example their charge state, and the bypass circuits 30, for example their state (active, passive), is displayed.

[0080] The positive pole 17 of each supercapacitor 12 is connected via a protection circuit 120 to its own input 112 of the control unit 110. The control unit 110 thus receives separate input signals that depend on the respective capacitor potential of the two supercapacitors 12. The protection circuit 120 has a voltage divider 122 with two series-connected resistors, a seventh resistor 123 and an eighth resistor 124. The voltage divider 122 is connected at one end to the positive pole 17 and at the other end to the zero potential UBO of the circuit arrangement 10. A node 125 of the voltage divider 122 is located between the resistors 123, 124. A capacitor 126 and a Zener diode 127 are connected in parallel to the eighth resistor 124. The Zener diode 127 and the capacitor 126 serve to protect the input 112 from voltage and to ensure electromagnetic compatibility (EMC).Node 125 of the voltage divider is connected to input 112 of control unit 110. Therefore, an input signal in the form of a potential is present at input 112 that is lower than the capacitor potential of the respective supercapacitor 12. Resistors 123, 124 of voltage divider 122 are matched to the maximum capacitor potential of the respective supercapacitor 12 such that a maximum of 5 V is present at input 112.

[0081] As described, the control unit 110 receives an input signal at each input 112. Since the resistance values ​​of the resistors 123, 124 of the respective voltage divider 122 are known, the respective capacitor potential and, due to the series connection, the capacitor voltage of the respective supercapacitor 12 can be determined from the input signal. If the capacitor voltages of the two supercapacitors 12 differ, the control unit 110 can prevent further charging of the supercapacitor 12 with the higher capacitor voltage. To do this, the bypass circuit 30 of the affected supercapacitor 12 is switched to the active state. First, the light-emitting diode 94 is activated by the control unit 110, whereupon it switches the phototransistor 98 on. This closes the switch 100.The base of the bypass transistors 42 is consequently pulled to the potential of the cathode, causing the bypass transistors 42 and also the display transistor 52 to be switched on, i.e., conductive. This places the bypass circuit 30 in the active state. After the bypass transistors 42 are switched on, a portion of the charging current flows past the supercapacitor 12 through the bypass transistor 42, thus no longer charging the supercapacitor 12.

[0082] The bypass circuits 30 further each include a fuse 32 arranged between the positive terminal 17 of the respective supercapacitor 12 and the bypass circuit 30. The fuses 32 interrupt the current flow between the supercapacitors 12 and the bypass circuit 30 in the event of an extreme overvoltage. If a fuse 32 is interrupted, the control unit 110 can detect this as a fault based on the input signals at its inputs 112. In such a fault, the control unit 110 can, for example, interrupt the charging process entirely, for example by switching a relay (not shown here) and thus interrupting the connection between the circuit arrangement 10 and a voltage source.

[0083] Figure 2 shows the circuit diagram of an electrical energy storage device 200. The energy storage device 200 comprises two circuit assemblies 10, which are constructed as shown in Figure 1 and arranged in a housing (not shown). The supercapacitors 12 of the two circuit assemblies 10 are all connected in series and are connected to an anode terminal 14 on the one hand and to a cathode terminal 16 on the other. A power source can be connected to the anode terminal 14 and the cathode terminal 16. A bypass circuit 30 is connected in parallel to each supercapacitor 12. Each circuit assemblies 10 has its own control unit 110. Each control unit 110 is assigned two supercapacitors 12 and associated bypass circuits 30.Each bypass circuit 30 is connected to the respective control unit 110 via two connections, wherein, as in Figure 1, one connection is connected to an input 112 of the control unit 110 and the other connection is connected to an output 114 of the control unit 110.

[0084] The control units 110 are electrically isolated from each other via a fiber optic cable 117. This allows the control units 110 to exchange information, for example, regarding the charge states of the individual supercapacitors 12.

[0085] The energy storage device 200 further comprises a communication unit 210. The communication unit 210 has several interfaces (not shown) by means of which communication with the communication unit 210 can take place from outside the energy storage device 200. The control units 110 are each connected to the communication unit 210 via an optical fiber 212, 214 with galvanic isolation.

[0086] The energy storage device 200 further comprises a display 220 connected to the communication unit 210. In particular, information that the communication unit 210 receives from the control units 110 can be displayed on the display 220.

[0087] List of reference symbols

[0088] 10 Circuit arrangement

[0089] 12 Supercapacitor

[0090] 14 Anode connection

[0091] 16 Cathode connection

[0092] 17 Positive pole

[0093] 18 Negative pole

[0094] 30 Bypass circuit

[0095] 32 fuse

[0096] 40 bypass line

[0097] 42 Bypass transistor

[0098] 44 first resistance

[0099] 46 third resistance

[0100] 50 display strands

[0101] 52 Display transistor

[0102] 54 LEDs

[0103] 56 fourth resistance

[0104] 60 regulator string

[0105] 62 cross controls

[0106] 63 controller nodes

[0107] 64 second resistance

[0108] 70 voltage divider string

[0109] 72 voltage dividers

[0110] 73 fifth resistance

[0111] 74 sixth resistance

[0112] 75 voltage divider nodes

[0113] 90 optocouplers

[0114] 92 Sending side

[0115] 94 LEDs

[0116] 96 Receiving side Phototransistor Switch Control unit Input Output Display Light guide Protection circuit Voltage divider Seventh resistor Eighth resistor Node Capacitor Zener diode Energy storage Communication unit Light guide Light guide Display

Claims

Patent claims 1. Circuit arrangement (10) with at least one supercapacitor (12) and a bypass circuit (30) connected in parallel to the supercapacitor (12), which in an active state prevents or limits the charging of the supercapacitor (12), wherein the bypass circuit (30) is in an inactive state below a predefined voltage threshold of a capacitor voltage applied to the supercapacitor (12) and is switched to the active state when the predefined voltage threshold is exceeded, characterized in that the bypass circuit (30) comprises a switch (100) controllable by a control unit (110), by means of which the bypass circuit (30) can be switched to the active state independently of the predefined voltage threshold.

2. Circuit arrangement (10) according to claim 1, characterized in that several supercapacitors (12) are connected in series, wherein a bypass circuit (30) according to claim 1 is connected in parallel to each supercapacitor (12) and wherein each switch (100) of the bypass circuits (30) can be controlled independently of the other switches (100).

3. Circuit arrangement (10) according to claim 2, characterized in that the control unit (110) is connected to the supercapacitors (12) in such a way that it can detect the capacitor voltage applied to the respective supercapacitor (12) and / or the capacitor potential applied to a positive terminal (17) of the respective supercapacitor (12).

4. Circuit arrangement (10) according to claim 3, characterized in that the positive terminal (17) of each supercapacitor (12) is connected to each input (112) of the control unit (110), whereby the control unit (110) receives an input signal in the form of a potential depending on the capacitor potential.

5. Circuit arrangement (10) according to claim 3 or 4, characterized in that a protection circuit (120) with a voltage divider (122) is arranged between each positive terminal (17) and the associated input (112) of the control unit (110), wherein the voltage divider (122) is connected at one end to the positive terminal (17) and has two resistors (123, 124) connected in series, between which a node (125) is arranged and wherein the input (112) of the control unit (110) is connected to the node (125).

6. Circuit arrangement (10) according to claim 5, characterized in that the resistors (123, 124) are adapted to the nominal maximum capacitor potential of the associated supercapacitor (12).

7. Circuit arrangement (10) according to claim 5 or 6, characterized in that the resistors (123, 124) of the voltage divider (122) are selected such that the potential applied to the respective input (112) of the control unit (110) is below a predetermined value.

8. Circuit arrangement (10) according to one of the preceding claims, characterized in that the bypass circuit (30) comprises at least one bypass transistor (42) operating as a switching element and connected in parallel to the supercapacitor (12), and a cross-regulator (62) connected in parallel to the supercapacitor (12), which, upon reaching its switching threshold, switches on the bypass transistor (42) and thereby puts the bypass circuit (30) into the active state.

9. Circuit arrangement (10) according to claim 8, characterized in that the bypass circuit (30) comprises a voltage divider (72) connected in parallel to the supercapacitor (12), the voltage divider node (75) of which is connected to a control input of the shunt regulator (62), wherein the voltage divider (72) defines that the shunt regulator (62) reaches its switching threshold when the predefined voltage threshold is reached.

10. Circuit arrangement (10) according to one of claims 8 or 9, characterized in that the switch (100) and the sequential regulator (62) are connected in parallel and independently switch the bypass transistor (42).

11. Circuit arrangement (10) according to one of the preceding claims, characterized in that the bypass circuit (30) comprises an optocoupler (90) with a transmitting side (92) and a receiving side (96), wherein the transmitting side (92) is connected to the control unit (110) and wherein the receiving side (96) forms the switch (100).

12. Circuit arrangement (10) according to one of the preceding claims, characterized in that several control units (110) are provided, each control unit (110) being equipped with at least one switch (100) of a bypass circuit (30) is connected and wherein adjacent control units (110) are connected to each other with galvanic isolation, in particular by an optical connection. Electrical energy storage device (200) with a housing and at least one circuit arrangement (10) arranged in the housing according to one of the preceding claims. Use of a circuit arrangement (10) according to one of claims 1 to 12 as an energy storage device (200) in a photovoltaic system, in a vehicle with an alternative drive, in a charging station for electric vehicles, in a buffer storage device of a wind turbine or in a mobile storage device. Method for operating a circuit arrangement (10) according to one of claims 1 to 12, characterized in that the control unit (110) controls the switch (100) of the bypass circuit (30) such that the bypass circuit (30) is set to the active state regardless of the predefined voltage threshold.A method for operating a circuit arrangement (10) according to claim 15, characterized in that the control unit (110) actuates the switches (100) of several bypass circuits (30) depending on the potentials applied to the inputs (112) of the control unit (110). A method according to claim 15 or 16, characterized in that the control unit (110) compares the potentials applied to the inputs (112) of several bypass circuits (30) with each other and, depending on the comparison, actuates the switches (100) of selected bypass circuits (30) and thereby puts the selected bypass circuits (30) into the active state.Method according to one of claims 15 to 17, characterized in that the control unit (110) converts the potentials applied to the inputs (112) of several bypass circuits (30) of the control unit (110) into comparison values ​​by means of a factor specified by the respective voltage divider (72), then compares the comparison values ​​of the bypass circuits (30) with each other and, depending on the comparison, controls the switches (100) of selected bypass circuits (30) and thereby puts the selected bypass circuits (30) into the active state. The system is put into a specific state, whereby the comparison determines in particular which supercapacitor (12) has the highest capacitor voltage and only the bypass circuit (30) belonging to this supercapacitor (12) is activated.

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