DE102022110861B3 - Circuit arrangement, electrical energy store, use of a circuit arrangement and method for operating a circuit arrangement - Google Patents

Abstract

Circuit arrangement (10) with a supercapacitor (12) and a bypass circuit (30) which is connected in parallel with the supercapacitor (12) and which, in an active state, prevents or limits charging of the supercapacitor (12). A switch (100) that can be actuated by a control unit (110) is provided, by means of which the bypass circuit (30) can be switched to the active state.

Description

The present invention relates to a circuit arrangement, an electrical energy store, the use of a circuit arrangement as an energy store and a method for operating a circuit arrangement.

Energy can be stored, among other things, by chemical conversion (e.g. in the case of accumulators) or by physical processes (e.g. in the case of capacitors).

Capacitors can be differentiated according to their design. For example, there are ceramic capacitors, plastic film capacitors, metal paper capacitors and electrolytic capacitors. These types of capacitors typically range in capacitance from picofarads (pF) to about 1 farad.

A special feature among the capacitors are the so-called supercapacitors. 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 and pseudo-capacitance. While double layer capacitance is based on charge separation, pseudocapacitance is the result of redox reactions. In operation, the double layer and pseudo capacitance add up to the total capacitance of the supercapacitor.

A special feature of supercapacitors is their low nominal voltage of usually 2.4 to 2.7 V compared to conventional capacitors. At the same time, supercapacitors are extremely sensitive to higher voltages. Exceeding the nominal voltage even slightly during the charging process can lead to permanent damage to the supercapacitor. If supercapacitors are integrated into electronic circuits, it therefore makes sense to protect them from higher voltages.

Since many applications require a voltage higher than 2.7 V, supercapacitors are often connected in series, which means that the nominal voltages add up. Due to the series connection, however, it can happen during the charging process that the individual supercapacitors are charged at different speeds. The reason for this is, in particular, manufacturing tolerances, as a result of which nominally identical supercapacitors actually have different capacitances. The resulting different charging behavior can cause individual supercapacitors to exceed the rated voltage and become permanently damaged.

To avoid damage to series-connected supercapacitors, the WO 2018/237320 A1 propose a balancing circuit in which each supercapacitor is assigned a bypass circuit. The bypass circuits are connected to a bus system and, when activated, cause a charge equalization between the series-connected supercapacitors. Activation is via a clock generator. The circuit is complex due to the use of a bus system and the clock generator. In addition, the clock causes only a periodic and not permanent charge equalization. This means that there is only temporary protection for the capacitors.

The 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 by which the supercapacitor is charged. Because of the detector unit and the control of the charging device, this bypass circuit is also very complex.

The DE 600 23 772 T2 discloses a circuit arrangement with a double-layer capacitor and a shunt regulator connected in parallel with the double-layer capacitor and 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.

The US 2020/0044459 A1 discloses an apparatus and method for protecting the batteries in a battery pack from being overcharged.

The DE 10 2011 053 013 A1 discloses a device and a method for balancing the voltage distribution of energy storage devices connected in series.

It has been shown that the known circuit arrangements for supercapacitors are inadequate and that deviations in the charging of the supercapacitors can also occur with these circuits.

It was therefore the object of the invention to improve the protection of supercapacitors during the charging process.

This object is achieved by the circuit arrangement according to the invention.

The circuit arrangement has at least one supercapacitor and a bypass circuit which is connected in parallel with the supercapacitor and 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 present at 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 control unit controllable switch, by means of which the bypass circuit can be set to the active state independently of the predefined voltage threshold, in particular from the inactive state to the active state.

If the bypass circuit is already in the active state as a result of the predefined voltage threshold being exceeded, then, strictly speaking, it is not put into the active state by an (additional) switching of the switch. In this case too, however, the switch is in any case suitable for switching the bypass circuit from the inactive state to the active state.

The bypass circuit is provided to protect the supercapacitor from overvoltage. When the bypass circuit is placed in the active state, it preferentially bypasses current around the supercapacitor. This current does not further charge the supercapacitor, so there is no overvoltage and the supercapacitor is protected. If no external voltage is applied to the circuit arrangement, that is to say if no current source is connected to the supercapacitor, then the bypass circuit, in its active state, will discharge the supercapacitor. In any case, electrical energy is converted into heat by a bypass circuit in an active state and is "lost", i.e. it is released into the environment.

The charging and discharging of supercapacitors, triggered by manufacturing tolerances and deviating degeneration, is not always completely identical. If supercapacitors connected in series are always fully charged, these problems are hardly noticeable. However, it has been recognized that, over time, there are ever-increasing deviations between the charge states of a number of supercapacitors connected in series if the supercapacitors are repeatedly incompletely charged and discharged. The invention therefore creates a possibility of putting the bypass circuit into the active state independently of the predefined voltage threshold and in this way 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 placed in the active state when the switch is closed. The switch is preferably a transistor, the closed state of the switch being when the transistor is turned on. Alternatively, other switches can also be used.

In advantageous developments, a plurality of supercapacitors are connected in series, with each supercapacitor having a bypass circuit connected in parallel as mentioned above, and with each switch of the bypass circuits being able to be controlled 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 placed in the active state as needed.

• - Doppelschichtkondensatoren besitzen Kohlenstoffelektroden oder deren Derivate mit einer sehr hohen statischen Doppelschichtkapazität. Der Anteil der faradayschen Pseudokapazität an der Gesamtkapazität ist nur gering.
• - Pseudokondensatoren besitzen Elektroden aus Metalloxiden oder aus leitfähigen Polymeren und haben einen sehr hohen Anteil faradayscher Pseudokapazität.
• - Hybridkondensatoren besitzen asymmetrische Elektroden, eine mit einer hohen Doppelschicht-, die zweite mit einer hohen Pseudokapazität.

Depending on the design of their electrodes, supercapacitors are divided into three different capacitor families:

• - Double layer capacitors have carbon electrodes or their derivatives with a very high static double layer capacitance. The proportion of the Faraday pseudo-capacity in the total capacity is only small.
• - Pseudocapacitors have electrodes made of metal oxides or conductive polymers and have a very high proportion of Faraday pseudocapacitance.
• - Hybrid capacitors have asymmetric electrodes, one with a high double-layer capacitance, the second with a high pseudocapacitance.

The supercapacitors of the circuit arrangement according to the invention are particularly preferably lithium titanate oxide supercapacitors (LTO supercapacitors). LTO supercapacitors belong to the hybrid capacitors. In LTO supercapacitors, the negative graphite electrode is replaced by a sintered electrode made of titanium spinel (Li ₄ Ti ₅ O ₁₂ ). With a factor of 30, the lithium titanate electrode has a significantly higher effective surface area than a graphite electrode. For this reason, very high charging and discharging currents in the range of more than 10C can be realized. The power density is therefore around 1,200-3,500W/kg (2,700-7,500W/litre). The high charge and discharge currents can lead to the deviations given above in the case of incomplete charging cycles. The circuit arrangement according to the invention is therefore particularly advantageous when using LTO supercapacitors.

In advantageous developments, the control unit is connected to the supercapacitors in such a way that it can detect the capacitor voltage present at the respective supercapacitor and/or the capacitor potential present at a positive pole of the respective supercapacitor. The capacitor voltage or the capacitor potential provide information about how large the deviation of the state of charge of several supercapacitors is. In this way, the control unit can determine which bypass circuit is to be placed in the active state. The positive pole of each supercapacitor is preferably connected to its own input of the control unit, as a result of which the control unit receives an input signal in the form of a potential depending on the capacitor potential actually present. By comparing the potentials, the control unit can determine the capacitor voltage of the respective capacitor and use this to determine the deviations in the state of charge. Alternatively, the capacitor voltage can also be recorded directly by a measuring unit and transmitted as information to the control unit. For this purpose, the measuring unit is connected to the supercapacitor and the control unit.

With supercapacitors connected in series, the capacitor potential adds up with each additional supercapacitor. It is desirable to protect the control unit inputs from excessively high potentials. A protective circuit with a voltage divider is therefore preferably arranged between each positive pole and the associated input of the control unit, the voltage divider being connected at one end to the positive pole and having two resistors connected in series, between which a node is arranged and the input of the control unit is connected to the node. As a result, the potential at the input of the control unit is lower than the capacitor potential of the respective supercapacitor. The other end of the voltage divider is preferably at a zero potential (U _B0 ) of the circuit arrangement. This zero potential does not have to correspond to the ground potential.

A connection of the control unit is preferably likewise at the zero potential of the circuit arrangement.

As already mentioned, the potential increases across the series-connected supercapacitors. It is therefore advantageous if the resistors are matched to the nominally maximum capacitor potential of the associated supercapacitor. The nominally maximum capacitor potential results from the nominal voltages of the supercapacitors connected in series and the position of the respective supercapacitor in the series connection, starting from the cathode. For example, if three supercapacitors with a nominal voltage of 2.7 V are connected in series, then, starting from the anode, the nominal maximum capacitor potential is 2.7 V for the first supercapacitor, 5.4 V for the second supercapacitor and 8 for the third supercapacitor. 1 v

It is particularly advantageous if the resistances of the voltage divider are selected in such a way 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 resistances of each voltage divider are selected in particular in such a way that the predetermined value is not exceeded at the nominally maximum capacitor potential of the associated supercapacitor.

The voltage threshold is preferably defined by the bypass circuit itself, in particular by its electronic components. In particular, it is not specified, influenced or even controlled from outside the bypass circuit.

In advantageous developments, the bypass circuit has at least one bypass transistor which operates as a switching element and is connected in parallel with the supercapacitor, and a quadrature regulator which is connected in parallel with the supercapacitor and which switches the bypass transistor through (becomes conductive) when its switching threshold is reached and thereby the bypass Switches circuit to the active state in which the bypass circuit directs current around the supercapacitor. A transverse regulator can generally be understood as a component which is connected in parallel with the supercapacitor and, at least in the active state, always draws so much current that the voltage across the supercapacitor is kept constant. In the bypass circuit, the quadrature 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 value (the threshold value). strides. In the present case, the measured variable is a variable of the circuit arrangement, namely the capacitor voltage present at the supercapacitor. The quadrature regulator is preferably switchable and has a control input for this purpose. For example, a TL431 (switchable) can be used as a cross regulator. The quadrature regulator can therefore also be referred to as a parallel regulator, shunt regulator or threshold switch.

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.

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 preferable for the bypass transistor to deliver a sufficiently high current, in particular >2 A, between collector and emitter even at low voltages, in particular at <2.7 V. In this way, the bypass transistor provides a good protective function for the supercapacitor.

The switching threshold is an intrinsic variable of the quadrature controller. If the quadrature regulator has a control input, then the switching threshold at the control input must be reached for the quadrature regulator to switch. With a TL431, the switching threshold is 1.5 V to 2.5 V.

During the charging process, the supercapacitor is first charged as usual using a charging current. The bypass circuit is in a passive (inactive) state as long as the switching threshold of the cross regulator is not reached. When the switching threshold is reached, the at least one bypass transistor is activated by the quadrature regulator. The bypass circuit is then in an active state. The bypass circuit shunts current around the supercapacitor in this condition. This current does not further charge the supercapacitor, so at least if the charging current of the supercapacitor is less than or equal to the current bypassed around the supercapacitor, an overvoltage will not occur. In any case, the amount of current charging the supercapacitor is reduced by the bypass circuit when active, thus protecting the supercapacitor.

The quadrature regulator preferably defines the switching point for the bypass transistor in that an output of the quadrature regulator is connected to a control input of each bypass transistor. A resistor is particularly preferably arranged between the output (anode connection) of the quadrature regulator and the input of each bypass transistor. The use of a resistor between the shunt regulator and the bypass transistor serves to compensate for tolerances and limit the maximum current of the base connection. The resistors ensure that the actual switching times of the bypass transistors, which always deviate due to tolerances, are not too far apart.

The amplification effect of transistors is not binary, but follows a characteristic curve and depends on the level of the voltage across the capacitor (base-emitter voltage) and/or a control signal. A higher base-emitter voltage increases the gain, i.e. the transistor is "turned on" further. When the control signal is low, the amplification effect of a transistor is reduced. Simple capacitors have higher nominal voltages compared to 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 turn on more and immediately conduct a higher current around the capacitor, protecting it very effectively. In the case of simple capacitors, bypass circuits thus achieve a sufficient bypass effect.

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 means that the control signal does not switch the transistors optimally and thus only a reduced current conduction, i. H. there is no optimal protection for the supercapacitors.

By placing at least two bypass circuits in parallel with the supercapacitor, more total current can be shunted around the supercapacitor. The bypass circuits are independent of each other. It is therefore possible to provide different switching points for the respectively controlled bypass transistor. In this way, the protection of the supercapacitor can, for example, also be switched on in several stages depending on the applied voltage.

A further improvement in the protective effect can be achieved by each bypass circuit comprising two bypass transistors which work as switching elements and are each connected in parallel with the supercapacitor threshold of the quadrature regulator defines the switching point for the two bypass transistors connected in parallel. The bypass transistors are preferably nominally identical. The two bypass transistors in this case are switched together and allow a higher current to be shunted around the supercapacitor.

The bypass circuit preferably also has an indicator transistor connected in parallel with the supercapacitor. The indicator transistor is also controlled by the quadrature regulator as soon as it reaches its switching threshold. In this way, the switching threshold of the quadrature 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 for tolerance compensation and current limitation of the maximum current of the base connection is arranged between the regulator node and the base of the display transistor. The display transistor can differ from the bypass transistor due to the further interconnection with the light-emitting diode. The resistance between the regulator node and the base of the display transistor is preferably chosen such that the display transistor switches at the same time as the bypass transistors. When the quadrature regulator reaches its switching threshold, it switches on the display transistor, whereupon the LED lights up, indicating that the bypass circuit is in its active state.

The bypass circuit preferably includes a voltage divider connected in parallel with the supercapacitor, whose voltage divider node is connected to a control input of the quadrature regulator, it being defined by the voltage divider that the quadrature regulator reaches its switching threshold when the predefined voltage threshold is reached at the supercapacitor. The voltage divider preferably has two resistors connected in series, 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 quadrature regulator reaches its switching threshold. In this way, different bypass circuits, for example for different supercapacitors, can be implemented with the same components, which means that production costs can be reduced. The node potential is then influenced depending on which switching point is desired or the capacitance of the supercapacitor connected in parallel.

The variable resistance arrangement preferably has a plurality of parallel partial strands, each with a different electrical resistance, and includes a selection means, with the selection means being able to select precisely one partial strand as the conductive partial strand or multiple partial strands being able to be selected as the conductive partial strands. The selection means makes it possible, in a simple manner, to select exactly that or those sub-strings from among the sub-strings which is/are the right ones for the supercapacitor to be used. The selection can be made by a fixed contact, for example by soldering, or a variable contact, for example by means of a changeover switch. If two bypass circuits are used for a supercapacitor and their quadrature regulators are to switch at different capacitor voltages, a first substring can be selected in one bypass circuit and a second substring in the other bypass circuit when using identical components. As a result, the node potentials of the two voltage dividers are always different and, as a result, the switching times of the quadrature regulators also deviate from one another. As a result, the different switching times of the two bypass circuits can be implemented in a simple manner.

As an alternative to a plurality of sub-strings, the variable resistor arrangement preferably includes a potentiometer. A potentiometer enables a stepless adjustment of the resistance and thus ultimately the switching time. A circuit arrangement with a potentiometer can thus be adapted more flexibly to requirements.

As described, the switch has an open and a closed state and preferably switches the bypass transistor through in the closed state. The switch and the quadrature regulator are particularly preferably connected in parallel and can switch through the bypass transistor independently of one another. If the quadrature control has already switched the bypass transistor through, pressing the switch has no effect. The switch is nevertheless suitable for turning on the bypass transistor independently of the voltage threshold.

The bypass circuit preferably comprises an optocoupler with a transmission side and a reception side, the transmission side being connected to the control unit and the reception side forming the switch. The transmitting side and the receiving side of an optocoupler can communicate with each other, that is, in particular, they can transmit signals, but they are electrically isolated from one another. Due to the different potentials of the various supercapacitors, it is advantageous to use a component with galvanic isolation between the control unit and the switch. It is also possible to use other components instead of the optocoupler, which bring about galvanic isolation, for example an isolating transformer or a relay.

The transmitting side of the optocoupler preferably has a light-emitting diode and the receiving side has a phototransistor. The light-emitting diode is driven by the control unit of the circuit arrangement. For this purpose, the light-emitting diode is connected to an output of the control unit. If the light-emitting diode is activated by the control unit ("HIGH level triggering"), it switches the phototransistor through, which means that the switch is conductive, i.e. in the closed state. If the light-emitting diode is deactivated, the switch is opened. In other words, the switch can be switched to the open state and the closed state depending on a signal from the transmission side.

The control unit preferably comprises at least one multiplexer, in particular a 74HC4067. The control unit particularly preferably includes a multiplexer, which forms the inputs for the input signals, and a multiplexer, which forms the outputs for the switches. The multiplexers are preferably connected to a central controller of the control unit, for example an Arduino Nano.

In advantageous developments, a plurality of control units are provided, each control unit being connected to at least one switch of a bypass circuit and adjacent control units being 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, ie 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, ie in particular in series and/or in parallel. In this way, an energy store is provided that is precisely tailored to the desired application.

The galvanically isolated connection of the control units takes place in particular by an optical connection, for example an optical waveguide. Each control unit is particularly preferably assigned a plurality of switches, with the control unit being able to activate the switches assigned to it independently of one another.

In advantageous 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.

The circuit arrangement can include one or more separate temperature sensors, which are connected to the control unit. In particular, a temperature sensor is associated with each supercapacitor and/or each bypass circuit. Depending on the signal from the temperature sensors, the control unit can switch the bypass circuit(s) to the active state.

As described, supercapacitors are subject to manufacturing-related tolerances (manufacturing tolerances). If several supercapacitors are connected in series in a circuit, the individual supercapacitors are charged 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 a number of capacitors in parallel, as a result of which the individual supercapacitors are better protected. In advantageous developments, at least two supercapacitors connected in parallel are therefore provided, which together form a supercapacitor group. In other words: several supercapacitors are connected in parallel and the bypass circuit is provided in parallel. Statistically, connecting several capacitors in parallel means that the supercapacitor group is less likely to deviate greatly from its nominal capacitance. Particularly preferably, the supercapacitors connected in parallel are nominally identical. Identical components have the same tolerance limits, which means that the statistical effect is particularly effective. The above description relating to series-connected supercapacitors applies equally to series-connected supercapacitor groups.

You may wish to pause the loading process. This is the case, for example, when all supercapacitors in the circuit arrangement are fully charged. As described, this state can be determined by the control unit using the input signals. The circuit arrangement preferably includes a switching element which is connected to the control unit and which is set up to provide the connection between a connection for a current source and the supercon to be able to disconnect and close the densator. The switching device is preferably a relay connected in series with the supercapacitors.

The object of the invention is also achieved by an electrical energy store with a housing and at least one circuit arrangement arranged in the housing according to the above description. The series-connected supercapacitors offer a higher voltage rating than is possible with a single supercapacitor. At the same time, deviations in the state of charge of the supercapacitors are avoided by the circuit arrangement according to the invention.

Particularly preferably, a plurality of circuit arrangements are connected in series, each having a plurality of supercapacitors connected in series. The energy store then advantageously makes the zero potential available for the first circuit arrangement in the series, for example through a connection to ground. All further circuit configurations have the respectively higher end potential of the preceding circuit configuration in the series as the zero potential. In an energy store with a nominal voltage of 75 V, for example, and three identical circuit configurations, the zero potential of the first circuit configuration is 0 V, the zero potential of the second circuit configuration is 25 V and the zero potential of the third circuit configuration is 50 V.

At least one temperature sensor, which detects the temperature in the housing, can be arranged in the housing. The temperature sensor is connected to the control unit.

The housing is preferably grounded.

The energy store preferably comprises at least one display which is connected to the control unit, in particular one which is electrically 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 the bypass Circuits and/or other information are displayed.

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

The object of the invention is also achieved through the use of a circuit arrangement as described above as an energy store in a photovoltaic system, in a vehicle with alternative drive, in a charging station for electric vehicles, in a buffer store of a wind turbine or in a mobile store. In the winter, in particular, in the case of a photovoltaic system, there are regularly incomplete charging processes during which, without the circuit arrangement according to the invention, there would be deviations in the states of charge of supercapacitors connected in series over time. These deviations are avoided by the invention. It can also happen that the programming of the inverter of the photovoltaic system makes a shutdown before the supercapacitors reach the voltage threshold. In this case, the supercapacitors will never be fully charged enough to reach the voltage threshold and switch the bypass circuits into the active state. Therefore, even in the case of a supposed full charge, the bypass circuits do not automatically equalize the charge. The circuit arrangement according to the invention is particularly advantageous in such cases, since it can also provide for an equalization of the charge states below the voltage threshold.

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 in such a way that the bypass circuit is switched to the active state independently of the predefined voltage threshold.

The control unit controls the switches of several bypass circuits, preferably as a function of the potentials present at the inputs of the control unit. As described above, the potentials provide information about which capacitor voltage is present at each supercapacitor and are therefore particularly suitable as a starting point for controlling the switches.

The control unit preferably compares the potentials of a plurality of bypass circuits present at the inputs of the control unit with one another, controls the switches of selected bypass circuits as a function of the comparison and thereby puts the selected bypass circuits into the active state. Advantageously, the control unit first calculates the potentials present at the inputs of the control unit using a plurality of bypass circuits a factor specified by the respective voltage divider into comparison values, then compares the comparison values of the bypass circuits with one another, controls the switches of selected bypass circuits depending on the comparison and thereby puts the selected bypass circuits into the active state. The values and arrangement of the resistors of the voltage divider are known. It is therefore possible to convert a potential present at a specific input of the control unit into the capacitor potential, which was previously reduced by the voltage divider. The capacitor voltage is then the difference between the capacitor potentials of two adjacent supercapacitors. In this way, the capacitor voltages of each supercapacitor can be determined as a reference value and then compared with one another.

Particularly preferably, the comparison is used to determine which supercapacitor has the highest charge (capacitor voltage) and only the bypass circuit associated with this supercapacitor is activated. In this way, only one supercapacitor is held up from charging, and all other supercapacitors can “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 switched to the active state.

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 of the supercapacitors would no longer be charged.

Placing a bypass circuit in the active state may depend on one or more conditions. For example, a bypass circuit can be set to the active state 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 switched to the active state after a certain difference in the capacitor voltages and/or a difference to a specific number of supercapacitors in the same row. The difference is preferably less than 10% of the nominal voltage and/or between 0.02 V and 0.2 V.

Within the scope of the method according to the invention, it is also possible to define a (higher) difference limit for the capacitor voltages, at which the control unit detects an error and, for example, causes an output in the form of an alarm signal, for example a red LED or an acoustic warning signal. Automatic, wireless sending of a message (e.g. email, SMS or push message) to a predefined recipient (e.g. service technician, owner, 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 by means of the relay, thereby stopping the charging of all supercapacitors.

• 1 einen Schaltplan einer Schaltungsanordnung
• 2 einen Schaltplan einer elektrischen Energiespeichers.

The invention is illustrated and explained below by way of example with reference to the figures. It shows

• 1 a circuit diagram of a circuit arrangement
• 2 a circuit diagram of an electrical energy storage device.

The one in the 1 The circuit arrangement 10 shown comprises two supercapacitors 12, which can be connected to a power source (not shown) and/or a consumer (not shown) via an anode connection 14 and a cathode connection 16. If a power source is connected, the supercapacitors 12 are charged; if a load is connected, the supercapacitors 12 are discharged. Due to tolerances, the charging and discharging does not take place completely identically, so that deviations between the charging states of the two supercapacitors 12 can occur over time and in particular in the case of multiple, incomplete charging and discharging.

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, ie 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 has on the other hand, at its positive pole 17, a maximum capacitor potential of 2*2.7 V=5.4 V.

A bypass circuit 30 is connected in parallel with the supercapacitor 12 . The bypass circuit 30 includes a plurality of strings, each connected in parallel with the supercapacitor 12: two bypass strings 40, an indicator string 50, a regulator string 60, and a voltage divider string 70. The strings are discussed in more detail below.

The bypass strands 40 are structurally identical and are each connected in parallel with the supercapacitor 12 . Therefore, only one bypass line 40 is described. The bypass branch 40 includes the load path of a bypass transistor 42, the load path being connected in series with a first resistor 44. The bypass transistor 42 is a pnp bipolar transistor.

The controller branch 60 includes the load path of a quadrature controller 62, the load path being connected in series with a second resistor 64. The cross regulator 62 is a TL431. This is a controllable quadrature regulator 62 with three connections, an anode connection, a cathode connection and a reference connection. The load path runs between the anode connection and the cathode connection.

The cathode connection of the quadrature regulator 62 is connected to the negative pole 18 of the supercapacitor 12 . A regulator node 63 , which is connected to the base of both bypass transistors 42 , is located between the anode connection of the quadrature regulator 62 and the second resistor 64 . A third resistor 46 for tolerance compensation is arranged between the controller node 63 and the base. If there is a voltage below the switching threshold between the reference connection and the anode connection of the cross regulator 62, the cross regulator 62 blocks. The base and the emitter of both bypass transistors 42 are then both at the potential of the positive pole 17. No current therefore flows on the base -Emitter path so that the bypass transistors are not switched through. If a current source is present at the anode terminal 14 and the cathode terminal 16, the supercapacitor 12 is charged. Below a voltage threshold of the capacitor voltage present at the supercapacitor 12, which is predefined by the switching threshold of the quadrature regulator 62, the bypass circuit 30 is therefore in an inactive state.

The voltage divider branch 70 has a voltage divider 72 . The voltage divider 72 includes 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 connection, i.e. the control input of the quadrature regulator 62. The ratio of the resistors 73, 74 defines the capacitor voltage at which the quadrature regulator 62 reaches its switching threshold and switches.

If the switching threshold of the quadrature regulator 62 is reached at its reference connection, the quadrature 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, as a result of which the bypass transistors 42 are switched through, ie become conductive. This puts the bypass circuit 30 in the active state. In this way, the switching threshold of the quadrature regulator 62 defines the switching point for the bypass transistors 42. After the bypass transistors 42 have switched, part of the charging current flows past the supercapacitor 12 through the bypass transistor 42 and in this way charges the supercapacitor 12 no more. The supercapacitor 12 is thus protected from overvoltage at least when the current flowing from the power source to the supercapacitor 12 does not exceed the current bypassed around the supercapacitor 12 by the bypass circuit 30 .

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

In the embodiment shown here, the bypass transistors 42 and the display transistor 52 are nominally of the same construction (similar in construction), just as the third resistors 46 are nominally of the same construction. As a result, the transistors 42, 52 all switch at approximately the same time. The bypass transistors 42 and the indicator transistor 52 may be different in other embodiments. In any case, the third resistors 46 are preferably connected to the respective transistors 42, 52 adjusted so that the transistors 42, 52 all switch at approximately the same time.

The circuit arrangement 10 also includes an optocoupler 90 which has a transmission side 92 with a light-emitting diode 94 and a reception side 96 with a phototransistor 98 as a switch 100 . The transmitting side 92 and the receiving side 96 are galvanically separated from each other. The light-emitting diode 94 is driven 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 U _B0 of the circuit arrangement 10 . The switch 100 is connected in parallel with the quadrature regulator 62 .

The control unit 110 is also connected to the zero potential U _B0 of the circuit arrangement 10 .

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

The positive pole 17 of each supercapacitor 12 is connected to a separate input 112 of the control unit 110 via a protective circuit 120 . In this way, the control unit 110 receives separate input signals which depend on the respective capacitor potential of the two supercapacitors 12 . The protective circuit 120 has a voltage divider 122 with two series-connected resistors, a seventh resistor 123 and an eighth resistor 124 on. The voltage divider 122 is connected to the positive pole 17 at one end and to the zero potential U _B0 of the circuit arrangement 10 at the other end. A node 125 of the voltage divider 122 is located between the resistors 123, 124. A capacitor 126 and a Z-diode 127 are connected in parallel with the eighth resistor 124. The zener diode 127 and the capacitor 126 serve to protect the input 112 against voltage and to ensure electromagnetic compatibility (EMC). The node 125 of the voltage divider is connected to the input 112 of the control unit 110 . Therefore, an input signal in the form of a potential is present at the input 112, which is lower than the capacitor potential of the respective supercapacitor 12. The resistors 123, 124 of the voltage divider 122 are adapted to the maximum capacitor potential of the respective supercapacitor 12 in such a way that at the input 112 maximum 5 V applied.

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 can be determined from the input signal and the capacitor voltage of the respective supercapacitor 12 can be determined based on the series connection. If the capacitor voltages of the two supercapacitors 12 differ from one another, the control unit 110 can prevent further charging of the supercapacitor 12 with the higher capacitor voltage. For this purpose, 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. As a result, the switch 100 is closed. The base of the bypass transistors 42 is consequently pulled to the potential of the cathode, as a result of which the bypass transistors 42 and also the display transistor 52 are switched through, ie become conductive. This puts the bypass circuit 30 in the active state. After the bypass transistors 42 have switched, part of the charging current flows past the supercapacitor 12 through the bypass transistor 42 and in this way no longer charges the supercapacitor 12 .

The bypass circuits 30 also each include a fuse 32 which is arranged between the positive pole 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 broken, the control unit 110 can recognize this as an error based on the input signals at its inputs 112 . In the event of such an error, the control unit 110 can, for example, interrupt the charging process as a whole, for example by switching a relay (not shown here) and thus interrupting the connection between the circuit arrangement 10 and a voltage source.

The 2 shows the circuit diagram of an electrical energy storage device 200. The energy storage device 200 comprises two circuit arrangements 10, which, as shown in FIG 1 constructed and arranged in a housing, not shown. The supercapacitors 12 of the two circuit arrangements 10 are all connected in series and connected to an anode connection 14 on the one hand and to a cathode connection 16 on the other hand. A current source can again be connected to the anode connection 14 and the cathode connection 16 .

A bypass circuit 30 is connected in parallel with each supercapacitor 12 . Each circuit arrangement 10 has its own control unit 110 . Two supercapacitors 12 and associated bypass circuits 30 are assigned to each control unit 110 . Each bypass circuit 30 is connected to the respective control unit 110 via two connections, where as in FIG 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 .

The control units 110 are connected to one another via an optical fiber 117 with galvanic isolation. In this way, the control units 110 can exchange information, for example on the state of charge of the individual supercapacitors 12.

The energy store 200 also includes a communication unit 210. The communication unit 210 has a plurality of interfaces (not shown), by means of which communication with the communication unit 210 can take place from outside the energy store 200. The control units 110 are each connected to the communication unit 210 via an optical fiber 212, 214 with galvanic isolation.

The energy store 200 also includes a display 220 which is connected to the communication unit 210 . In particular, information which the communication unit 210 receives from the control units 110 can be displayed on the display 220 .

Reference List

10

circuit arrangement

12

supercapacitor

14

anode connection

16

cathode connection

17

positive pole

18

negative pole

30

bypass circuit

32

fuse

40

bypass line

42

bypass transistor

44

first resistance

46

third resistance

50

display line

52

display transistor

54

led

56

fourth resistance

60

controller line

62

cross control

63

controller node

64

second resistance

70

voltage divider string

72

voltage divider

73

fifth resistance

74

sixth resistance

75

voltage divider node

90

optocoupler

92

sending side

94

led

96

receiving side

98

phototransistor

100

Switch

110

control unit

112

Entry

114

Exit

116

screen

117

light guide

120

protection circuit

122

voltage divider

123

seventh resistance

124

eighth resistance

125

node

126

capacitor

127

zener diode

200

energy storage

210

communication unit

212

light guide

214

light guide

220

screen

Claims (18)

Circuit arrangement (10) with at least one supercapacitor (12) and a bypass circuit (30) which is connected in parallel with the supercapacitor (12) and which, in an active state, prevents or limits charging of the supercapacitor (12), the bypass circuit ( 30) below a predefined voltage threshold a capacitor voltage applied to the supercapacitor (12) is in an inactive state and is switched to the active state when the predefined voltage threshold is exceeded, characterized in that the bypass circuit (30) has a switch (100) that can be controlled by a control unit (110) includes, by means of which the bypass circuit (30) can be set independently of the predefined voltage threshold in the active state. Circuit arrangement (10) after claim 1 , characterized in that a plurality of supercapacitors (12) are connected in series, each supercapacitor (12) each having a bypass circuit (30). claim 1 is connected in parallel and wherein each switch (100) of the bypass circuits (30) can be controlled independently of the other switches (100). Circuit arrangement (10) after claim 2 , characterized in that the control unit (110) is connected to the supercapacitors (12) in such a way that it measures the capacitor voltage present at the respective supercapacitor (12) and/or the capacitor potential present at a positive pole (17) of the respective supercapacitor (12). can capture. Circuit arrangement (10) after claim 3 , characterized in that the positive pole (17) of each supercapacitor (12) is connected to a respective 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. Circuit arrangement (10) after claim 3 or 4 , characterized in that a protective circuit (120) with a voltage divider (122) is arranged between each positive pole (17) and the associated input (112) of the control unit (110), the voltage divider (122) being connected at one end to the positive pole (17) and has two series-connected resistors (123, 124) between which a node (125) is arranged and wherein the input (112) of the control unit (110) is connected to the node (125). Circuit arrangement (10) after claim 5 , characterized in that the resistors (123, 124) are adapted to the nominally maximum capacitor potential of the associated supercapacitor (12). Circuit arrangement (10) after claim 5 or 6 , characterized in that the resistors (123, 124) of the voltage divider (122) are selected in such a way that the respective potential at the input (112) of the control unit (110) is below a predetermined value. Circuit arrangement (10) according to one of the preceding claims, characterized in that the bypass circuit (30) has at least one bypass transistor (42) operating as a switching element and connected in parallel with the supercapacitor (12) and one bypass transistor (42) connected in parallel with the supercapacitor (12). Cross regulator (62), which turns on the bypass transistor (42) when its switching threshold is reached and thereby puts the bypass circuit (30) into the active state. Circuit arrangement (10) after claim 8 , characterized in that the bypass circuit (30) comprises a voltage divider (72) connected in parallel with the supercapacitor (12), the voltage divider node (75) of which is connected to a control input of the quadrature regulator (62), the voltage divider (72) defining is that the quadrature regulator (62) reaches its switching threshold when the predefined voltage threshold is reached. Circuit arrangement (10) according to one of Claims 8 or 9 , characterized in that the switch (100) and the quadrature regulator (62) are connected in parallel and switch through the bypass transistor (42) independently of one another. Circuit arrangement (10) according to one of the preceding claims, characterized in that the bypass circuit (30) comprises an optocoupler (90) with a transmission side (92) and a reception side (96), the transmission side (92) being connected to the control unit ( 110) and wherein the receiving side (96) forms the switch (100). Circuit arrangement (10) according to one of the preceding claims, characterized in that a plurality of control units (110) are provided, each control unit (110) being connected to at least one switch (100) of a bypass circuit (30) and adjacent control units (110 ) are connected to each other with galvanic isolation, in particular by an optical connection. Electrical energy store (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 until 12 as an energy store (200) in a photovoltaic system, in a vehicle with an alternative drive, in a charging station for electric vehicles, in a buffer storage of a wind turbine or in a mobile storage. Method for operating a circuit arrangement (10) according to one of Claims 1 until 12 , characterized in that the control unit (110) controls the switch (100) of the bypass circuit (30) in such a way that the bypass circuit (30) is switched to the active state independently of the predefined voltage threshold. Method for operating a circuit arrangement (10). claim 15 , characterized in that the control unit (110) controls the switches (100) of a plurality of bypass circuits (30) as a function of the potentials present at the inputs (112) of the control unit (110). procedure after claim 15 or 16 , characterized in that the control unit (110) compares the potentials of a plurality of bypass circuits (30) present at the inputs (112) of the control unit (110) and, depending on the comparison, the switches (100) of selected bypass circuits (30) controls and thereby puts the selected bypass circuits (30) in the active state. Procedure according to one of Claims 15 until 17 , characterized in that the control unit (110) converts the potentials of a plurality of bypass circuits (30) present at the inputs (112) of the control unit (110) into comparative values using a factor specified by the respective voltage divider (72), then the comparative values of the bypass circuits (30) are compared with one another and depending on the comparison the switches (100) of selected bypass circuits (30) are actuated and thereby the selected bypass circuits (30) are put into the active state, with the comparison in particular determining which supercapacitor (12) has the highest capacitor voltage and only the bypass circuit (30) associated with this supercapacitor (12) is activated.

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