DE20023503U1 - Circuit for generating voltage pulses, applying to fuel cell has arrangement for switching capacitance in charging/discharge circuit while/after voltage being applied - Google Patents

Abstract

The circuit has a pulse generator (30) for generating voltage pulses, a charge/discharge circuit (11/12) connected to the pulse generator containing at least one fuel cell (51) and capacitance (13) and a switch arrangement (20) for switching the charge/discharge circuit in relation to the capacitance in a charging circuit (11) while the voltage is being applied and in a discharge circuit (12) after applying the voltage. Independent claims are also included for the following: fuel cell system and the use of a fuel cell system, especially in a motor vehicle.

Description

The present invention relates to generally a circuit arrangement for generating voltage pulses and to imprint the voltage pulses on a fuel cell and a fuel cell system.

Fuel cells have been around since long known and especially in the automotive industry has grown significantly in importance in recent years.

In a fuel cell, for example a PEM fuel cell, electricity is generated by a chemical reaction generated. This is a fuel such as hydrogen and an oxidizing agent such as oxygen in electrical Energy and a reaction product such as water converted. A fuel cell essentially consists of an anode part, a membrane and a cathode part. The membrane consists of a gas-tight and proton conductive material and is between the anode and the Cathode arranged to exchange ions. On the side of the anode the fuel supplied while the oxidizing agent is supplied on the side of the cathode. At the anode, protons, i.e. Hydrogen ions are generated that pass through the membrane to the cathode move. At the cathode, the hydrogen ions react with the oxygen, and water forms. The electrons released during the reaction can be conducted as electrical current through a consumer, for example the electric motor of an automobile.

If you want the fuel cell with an easily available or fuel to be stored such as natural gas, methanol, gasoline or To operate the same, one must arrange these hydrocarbons in one arrangement to generate / process a fuel first in a hydrogen-rich Convert gas. This essentially produces hydrogen, carbon dioxide and to some extent carbon monoxide (CO), which is harmful to the fuel cell Represents gas and therefore before the fuel enters the fuel cell preferably should be largely removed.

In the fuel cell, the carbon monoxide Above a certain concentration, the Fuel cell output reduced and consequently the Efficiency of the fuel cell is greatly reduced.

In order to prevent such a harmful influence of carbon monoxide (CO) on the fuel cell, the DE 197 10 819 C1 , the disclosure content of which is included in the present application, a fuel cell has been described in which performance losses due to impurities absorbed on the anode catalyst are to be avoided. This is achieved in that the fuel cell is connected to means which impart a positive voltage pulse to the anode of the fuel cell. The voltage pulse causes a pulse-like change in the anode potential, which leads to the carbon monoxide in the fuel cell being oxidized. The voltage pulses can be impressed on the fuel cell by temporarily connecting an external DC voltage source to the fuel cell via a switch.

In the DE 197 10 819 C1 Although it has already been described in a general manner that the oxidation of carbon monoxide can advantageously take place by applying voltage pulses to the fuel cell. However, the example of a circuit arrangement provided for this purpose still has a number of disadvantages. For example, the electrical energy that is used to impress the voltage pulse on the fuel cell can no longer be used and is therefore lost. A separate external voltage source is also always required to provide the electrical energy for generating the voltage pulse. Finally, it is not possible with the known circuit arrangement to control or regulate the voltage pulses impressed on the fuel cell in terms of their size and shape, in order to be able to adapt them to different operating states and operating situations.

Starting from the one in the DE 197 10 819 In the prior art described, the present invention is based on the object of providing an improved circuit arrangement and an improved fuel cell system with which the disadvantages described above can be avoided in particular.

This task is done according to the first Aspect of the invention solved by a circuit arrangement for generating voltage pulses and to imprint the voltage pulses on a fuel cell, using a pulse generator to generate the voltage pulses, one connected to the pulse generator Charge / discharge circuit in which at least one fuel cell and at least a capacity is provided and with a switch arrangement for switching the charging / discharging circuit in terms of capacity into a loading circuit or an unloading circuit.

Through the circuit arrangement according to the invention it becomes possible on the one hand To be able to impress voltage pulses on a fuel cell, which causes the above described advantages with regard to the oxidation of harmful Substances such as carbon monoxide can be achieved. The Voltage pulses are advantageously the anode of the fuel cell impressed.

This imprint creates a pulse-like change of the anode potential.

The pulse generator provided in the circuit arrangement enables the To be able to regulate or control voltage pulses so that, depending on the operating situation and operating condition, voltage pulses of different sizes and shapes can be generated and impressed on the fuel cell.

Eventually it will be through use a capacity possible in the loading / unloading circuit, to store electrical energy. If the fuel cell, in particular the anode, voltage pulses are impressed, increases their anode potential. At the same time, the terminal voltage of the Fuel cell decreases because electricity is drawn from the fuel cell becomes. These electrical charges can be stored by the capacity become. about the fuel cell polarizes the voltage pulses as long as until the potential to oxidize the harmful substances, for example of carbon monoxide. Carbon monoxide is inside the anode compartment of the fuel cell, it can be oxidized, which leads to detoxification of the fuel cell.

To be able to load the capacity, the charge / discharge circuit above the switch arrangement during the voltage pulse impression switched such that it has a capacity Charging circuit forms. By using at least one capacitor is achieved in that the imposition of voltage pulses the electrical charges released are not lost, but can continue to be used. To be able to use these charges, what a discharge of capacity corresponds, the switch arrangement is switched in such a way after the voltage pulse impression, that the charging / discharging circuit functions as an discharging circuit.

Preferred embodiments of the circuit arrangement according to the invention result from the subclaims.

Can be advantageous in the discharge circuit a load may be provided. The load stored in the capacity can be connected to this load Energy are given off. The invention is not limited to this Designs of the load limited.

For example, it is conceivable that the load as a load resistor and / or other usable electrical Consumer is trained. If the load is designed as a load resistor is the capacity with embossing of voltage pulses are loaded onto the fuel cell and then via the load resistor unloaded again. The transmitted electrical Charge is converted into heat in the load resistor. However, it is also possible, the in capacity to use stored energy wisely. This can take the place load resistance is a useful one Consumers such as a rechargeable battery or the like then kick over the capacity can be loaded. In view of the present invention however, any other suitable consumer is also conceivable.

The capacitance can preferably be used as an UltraCap capacitor be trained. Such capacitors, which are in themselves from the state are known in the art in addition to a high capacity also over a particularly high power density. They are therefore suitable within large amounts of energy in short times to save or to be able to deliver.

The pulse generator can be advantageous designed to generate substantially rectangular voltage pulses his. Such voltage pulses, which are preferably designed as positive voltage pulses are, enable due to their steep flanks, particularly precise switching within the Circuitry.

The voltage pulses can advantageously have a variable pulse duration and / or a variable pulse interval. The definition of these terms results from the 1 , which schematically shows the course of the voltage over time. The pulse duration of the voltage pulse is denoted by D and the pulse interval is the time interval between two pulses by A. The letter F in 1 denotes the pulse rate. The time interval (period) between the start of a pulse and the start of the immediately following pulse corresponds to the reciprocal of the pulse frequency F. The invention is not limited to specific pulse durations, pulse intervals or pulse frequencies. Advantageous pulse durations can range, for example, in the range between 10 msec and 2 sec, preferably in a range between 100 and 500 msec. Examples of suitable pulse intervals are in the range between 2 and 7 seconds, advantageously between 4 and 5 seconds.

The pulse generator can be advantageous a circuit for calibrating the pulse duration of the voltage pulses exhibit. When using such a circuit, the pulse frequency for example, be fixed. Also the pulse duration and the pulse interval are essentially fixed. About the circuit is only the pulse duration calibrated, which means that a fine adjustment the pulse duration can be made. With this embodiment is a largely "rigid" option for generating voltage pulses.

In a further embodiment, the Pulse generator a circuit for variably setting the ratio from pulse duration to pulse spacing of the voltage pulses. By such a circuit will make it possible that within the pulse rate, which in turn can be fixed can, the ratio, which is also called duty cycle, between pulse duration and pulse interval can be set arbitrarily.

The setting of the pulse duration and / or the pulse interval described with regard to the two circuits mentioned can be carried out, for example, using one or more potentiometers. Potentiometers are known from the prior art known. These are continuously adjustable electrical resistors that have a sliding contact for tapping part resistors. Potentiometers can be designed, for example, as sliding or rotating resistors.

In a further embodiment, the Pulse generator a counter module have with the circuit for calibration of the pulse duration connected is. With the help of such a counter module and a like The corresponding circuit described above can supply the required voltage pulses be generated. The counter module can for example about have a so-called "clock input" via the the outgoing signals from the circuit in the counter module be fed. With counter modules, which are known per se from the prior art generally about sequential circuits for counting pulses.

In an advantageous embodiment can the pulse generator one or both of the aforementioned Have circuits. In the latter case, it becomes possible to apply voltage pulses set with any pulse duration and pulse interval to be able to. When using both circuits, the pulse generator can be advantageous a switch element for switching between the two Have circuits. The invention is not limited to this Switch element types limited. For example, the switch element as a transistor circuit or the like.

In a further embodiment, the Switch arrangement for the circuit of the charge / discharge circuit a driver element and one or have several transistors. When using such a switch arrangement can generated in the two circuits described above First impulses be switched to the driver element. The driver element provides for an overlap-free and switching the transistor (s) between charging and capacity discharge cycle.

The one or more transistors can be advantageous as field effect transistors, for example as MOSFET transistors, be trained.

That in the switch arrangement for the circuit of the charging / discharging circuit provided driver element can be like a Toggle switches act, the individual transistors conductive and turns off other transistors. This is supposed to be based on a concrete Example explained become.

For example, the switch arrangement can be a Have driver element and two transistors. To voltage pulses stamp on the fuel cell to be able can one of the transistors over the driver element is turned on while the other transistor is turned off. This will cause the charge / discharge circuit in converted to a pure charging circuit so that the capacity, for example the UltraCap capacitor, can be charged. By embossing the Voltage pulses, for example on the anode of the fuel cell, increase the anode potential, at the same time reducing the terminal voltage and electricity is drawn from the fuel cell. These electrical Charges are in capacity saved. The capacity can then if no voltage pulses are impressed, be discharged. To do this, the transistors are over the driver element is switched such that the initially conductive Transistor blocks and that the previously blocking transistor is conductive is switched. This makes the charging / discharging circuit cleaner Discharge circuit designed so that the capacity is discharged and the one stored in the capacity electrical energy for any consumer or load resistor can be used can.

Can be advantageous in the discharge circuit an arrangement for temporal smoothing the during the discharge of the capacity over the Load delivered electrical current may be provided. Such smoothing of the electricity is usually required when over the in capacity stored electrical charge usable consumers are operated should. Usually the loading or unloading takes place along a capacity of a non-linear curve Course. However, such a discharge curve is for downstream ones Consumers often not very suitable. By an appropriate arrangement for smoothing the of capacity emitted current can be achieved that the emitted by the capacity Energy according to the needs of the downstream consumer in a "stretched" form to disposal is provided.

According to the second aspect of the present The invention provides a fuel cell system with a or more fuel cells and one as described above circuit arrangement according to the invention for generating voltage pulses and for at least temporarily impressing the Voltage pulses on the fuel cell (s).

In such a fuel cell system according to the invention, it can initially be achieved in a simple manner that poisoning of the fuel cell (s) by carbon monoxide or the like therein is prevented or reversed by the application of voltage pulses. Furthermore, the electrical charges released during the application of the voltage pulses from the fuel cell (s) can be temporarily stored and then made available to any consumer. Finally, it is possible to be able to impress voltage pulses on the fuel cell (s), which are adapted to a prevailing operating situation. Regarding the advantages, effects, effects and the mode of operation of the fuel cell system according to the invention, reference is also made to the above statements regarding the circuit arrangement according to the invention full reference and hereby referenced.

Advantageous designs of the fuel cell system according to the invention result from the subclaims.

The pulse generator can advantageously be connected to one or more fuel cells in order to obtain the electrical energy required to generate the voltage pulses. In this way, a separate power source in the form of a battery, such as, for example, in relation to the DE 197 10 819 was described, be waived. In such a configuration of the fuel cell system, the energy required to generate the voltage pulses can be provided by the fuel cell system itself.

However, it is also possible that the pulse generator for reference to the generation of the voltage pulses required electrical energy is connected to a battery. Such Embodiment of the fuel cell system is, for example, during the Startup process, that is while the startup of the fuel cell system, an advantage. During the The fuel cell does not yet produce sufficient starting power Dimensions electrical Energy. However, the situation can occur precisely in this phase, that the fuel cell with an increased carbon monoxide content or other pollutants. In this case, you can use the additional Battery even during voltage pulses during the starting process of the fuel cell system the fuel cell (s) are imprinted, so that detoxification of the fuel cell (s) via the oxidation of the harmful Fabrics due to the changing Potential, especially the anode potential, within the fuel cell anytime possible is.

The fuel cell system can be advantageous or several fuel cell modules, each with one or more Have fuel cells. Usually fuel cell systems do not consist of only one fuel cell but from a variety of fuel cells. Thereby several Fuel cells assembled into so-called fuel cell stacks. The Fuel cell system can over have one or more such fuel cell stacks that then be assembled as individual fuel cell modules to form an overall system.

It is advantageous if that of the circuit arrangement generated voltage pulses to only one Part of the fuel cell modules or fuel cells independently of other fuel cell modules or fuel cells of the fuel cell system. Such an arrangement of the fuel cell system for a number of advantages. When the voltage pulses on the fuel cell (s) are imprinted be leads this does increase the potential, for example the anode potential, within the Fuel cell, but also to reduce the fuel cell terminal voltage. If now all fuel cells of the fuel cell system at the same time if the voltage pulses were applied, this could be brief total loss of the fuel cell system. If fuel cells to drive electrical consumers, for example Drive electric motors used in an automobile would be a such, if only brief, total failure of the fuel cell system or but also only a short-term significant loss in performance of the fuel cell system of considerable disadvantage.

If only single fuel cell modules independently voltage pulses from each other, this leads that such short-term total failures only ever occur in a small amount Part of the fuel cell system occur, so that the performance of the entire system can be kept to a minimum.

Furthermore, such a trained Fuel cell system always such fuel cell modules that voltage pulses are not currently being used are used to generate electrical energy to generate voltage pulses for such To provide fuel cell modules, which corresponding voltage pulses imprinted for detoxification should be.

One can advantageously be as above described circuit arrangement according to the invention for embossing of voltage pulses on one or more fuel cells in one Fuel cell system, in particular one as described above fuel cell system according to the invention, be used. Such a fuel cell system can be advantageous in or for a vehicle can be used.

Because of the rapid development Fuel cell technology in the vehicle sector offers one Currently particularly good uses. Still are too other uses conceivable. One example is fuel cells for mobile Devices like Computers or the like to stationary facilities such as power plants. Here the fuel cell technology is particularly suitable for the decentralized Energy supply of houses, Industrial plants or the like.

Preferably the present invention used in connection with fuel cells with polymer membranes (PEM). These fuel cells have a high electrical efficiency, cause only minimal emissions, show optimal part-load behavior on and are essentially free of mechanical wear. Also work them on one for the mobile use advantageous temperature level.

The invention will now be exemplified using exemplary embodiments under Be access to the accompanying drawing explained. Show it:

1 the schematic time course of voltage pulses that can be impressed on a fuel cell,

2 a circuit arrangement according to the invention in schematic form,

3 in a schematic view the structure of a pulse generator provided in the circuit arrangement and

4 an inventive fuel cell system.

In 2 is a circuit arrangement 10 for generating voltage pulses 40 and to impress the voltage pulses 40 on one or more fuel cells 51 a fuel cell system 50 (please refer 4 ). For the sake of clarity, is in 2 just a single fuel cell 51 shown.

The circuit arrangement 10 has a pulse generator 30 on who in connection with 3 is described in more detail and the substantially rectangular voltage pulses 40 generated. The voltage pulses 40 point out how this in 1 is shown, a defined pulse frequency F, a pulse duration D and a pulse interval A.

According to 3 can generate the square wave voltage pulses 40 done in different ways. First, the pulse generator 30 via an electrical line 31 supplied with electrical energy in the form of rectangular voltage pulses 40 to be converted. These are in the pulse generator 30 one circuit each 33 and a circuit 34 provided via a switch element 35 can be controlled optionally.

When switching 33 is such a circuit in which the pulse duration D can be calibrated, that is to say finely adjusted, at a predetermined pulse frequency F and an essentially predetermined pulse duration D and pulse interval A. The calibration or fine adjustment can be carried out, for example, using one or more potentiometers (not shown). The signals set in this way are via a clock input 37 a counter block 36 made available. In this way, the voltage pulses are converted into rectangular voltage pulses 40 can be converted with the desired pulse duration D and the desired pulse interval A. With a corresponding position of a second switch element 38 the voltage pulses generated in this way 40 via an electrical line 32 from the pulse generator 30 dissipated and other components of the circuit arrangement 10 are fed.

With the switch elements in the reverse position 35 and 38 however, it is also possible to use the rectangular voltage pulses 40 about the circuit 34 to create. The circuit 34 can be designed using one or more potentiometers (not shown) such that the ratio (duty cycle) of the pulse duration D to the pulse interval A can be varied and set as desired within a predetermined pulse frequency F. About the circuit 34 it is thus possible to generate voltage pulses with any pulse duration and pulse interval.

Coming back on 2 the voltage pulses generated in this way 40 from the pulse generator 30 to a charge / discharge circuit 11 . 12 the circuit arrangement 10 given. This is done via a switch arrangement 20 , In the loading / unloading circuit 11 . 12 are one or more fuel cells 51 arranged. Furthermore, is in the loading / unloading circuit 11 . 12 a capacitance designed as a UitraCap capacitor 13 intended.

The switch arrangement 20 has a driver element 21 as well as two transistors 22 . 23 , which are preferably designed as field effect transistors. About the driver element 21 can the transistors 22 . 23 either switched on or off.

The functioning of the circuit arrangement is now described below 10 described. If the fuel cell 51 with tension pulses 40 is to be acted upon, the driver element 21 controlled such that the transistor 22 conductive and the transistor 23 is turned off. This will make the charge / discharge circuit 11 . 12 in terms of capacity 13 as a pure charging circuit 11 connected. The fuel cell 51 is, so to speak, about the capacity 13 short-circuited. The voltage pulses 40 are thus about that of the driver element 21 to the transistor 22 given control signals indirectly to the fuel cell 51 impressed. This increases the fuel cell potential, for example the anode potential, which at the same time reduces the terminal voltage of the fuel cell 51 leads because electricity from the fuel cell 51 is pulled. Due to the changing potential in the fuel cell 51 Existing carbon monoxide will be oxidized, leaving the fuel cell 51 is detoxified.

Because the transistor 23 is turned off by the in the fuel cell 51 ongoing operations of the capacitor 13 loaded. That when impressing the voltage pulses 40 on the fuel cell 51 thus released electrical charges are not lost, but can in the capacitor 13 be cached.

To the capacitor 13 To be able to discharge later will be the switch arrangement again 20 actuated. This is the driver element 21 switched such that the transistor 22 blocking and the transistor 23 is switched on. This will make the charge / discharge circuit 11 . 12 as a pure discharge circuit 12 switched so that the capacitor 13 discharge and the electrical charge of a load stored therein 14 can be made available. In the present embodiment according to 2 is the burden 14 shown as load resistance. The electric la dung from the capacitor 13 is in this load resistance 14 converted into heat. However, the load is also conceivable 14 in the form of a meaningful consumer such as a rechargeable battery or the like, so that the in the capacitor 13 stored energy can be used sensibly when it is discharged.

In 4 is a fuel cell system after all 50 shown in which a circuit arrangement according to the invention as described above 10 is provided. The fuel cell system 50 has a number of fuel cells 51 on. For the sake of simplicity, there are only three fuel cells in the present example 51 shown. In practice, such fuel cell systems have 50 usually a number of fuel cell modules, each fuel cell module usually consisting of a number of fuel cells, which are combined into so-called fuel cell stacks. Such fuel cell systems 50 can be used, for example, to provide electrical energy for operating an electrical drive in a motor vehicle or the like. The individual fuel cells 51 are with leads 52 and derivatives 53 connected via which a suitable fuel and a suitable oxidizing agent is supplied or removed. For the sake of simplicity, the lines for the fuel and the lines for the oxidizing agent have not been shown separately from one another. The individual fuel cells 51 can be designed as so-called PEM fuel cells and have a cathode, an anode and an intermediate membrane. To in the presence of harmful carbon monoxide concentrations or other substances in the fuel cells 51 The individual fuel cells are able to bring about detoxification 51 with a circuit arrangement as described above 10 connected, via the substantially rectangular voltage pulses 40 on the anodes of the fuel cells 51 can be imprinted. The one for generating the voltage pulses 40 required electrical energy for the pulse generator 30 in the circuit arrangement 10 is about the fuel tents 51 provided itself. The individual fuel cells 51 via appropriate electrical connection lines 55 with the feeding electrical connection line 31 of the pulse generator 30 connected. The individual from the fuel cells 51 laxative electrical connection lines 55 are via a suitable switch element 56 with the electrical wire 31 connected. In this way it can be selected which of the fuel cells 51 each to provide the electrical energy for the pulse generator 30 is used. Similarly, that of the circuitry 10 generated voltage pulses 40 on the fuel cells 51 be imprinted. To do this, the voltage pulses 40 about that from the circuitry 10 laxative electrical wire 32 a switch element 59 and via corresponding electrical connecting lines 60 that with the switch element 59 are connected to the respective fuel cells 51 impressed. By using such a switch element 59 it becomes possible for individual fuel cells 51 targeted with the tension pulses 40 can be applied.

In 4 is still a battery 54 shown. The battery 54 is via an electrical connection line 57 and a switch element 58 with the circuit arrangement 10 connected.

The mode of operation of the arrangement described above is now explained below. Especially during the start phase of the fuel cell system 50 the situation may arise that the individual fuel cells 51 not yet generate sufficient electrical energy, but nevertheless the individual fuel cells 51 be poisoned with too high concentrations of carbon monoxide. To detoxify the fuel cells even in this condition 51 to be able to reach is the battery 54 intended. This battery 54 then provides the total of the electrical energy required to generate the voltage pulses to the individual fuel cells 51 should be imprinted. By switching the switch element accordingly 58 will be from the battery 54 generated voltage on the circuit arrangement 10 connected. The circuit arrangement 10 can then immediately generate the voltage pulses that the individual fuel cells 51 are imprinted so that they are detoxified due to a change in the fuel cell potential, which leads to an oxidation of the carbon monoxide. If the fuel cells 51 generate enough electrical energy so that the generation of the voltage pulses 40 about that from the fuel cells 51 generated electrical energy can take place, the switch element 58 be switched (as in 4 shown) that the generation of the voltage pulses 40 about the circuit arrangement 10 he follows.

By using the switch elements 56 and 59 it becomes possible that the individual fuel cells 51 , or the individual fuel cell modules, independently of one another with voltage pulses 40 can be applied. Would all fuel cells 51 simultaneously with the voltage pulses 40 applied, this would lead to a short-term total failure of the fuel cell system 50 lead, which is a considerable disadvantage. Due to the fact that only individual fuel cells 51 or fuel cell modules with voltage pulses 40 be charged while the remaining fuel cells 51 or continue running fuel cell modules in normal operation, it is achieved that the entire fuel cell system 50 shows a minimal, not noticeable drop in performance, if only one at a time fuel cells 51 or detoxify fuel cell modules.

By using a switch element 56 on the other hand, it ensures that the circuitry 10 about the fuel cells 51 is always supplied with sufficient electrical energy. If that for the circuit arrangement 10 required electrical energy via the fuel cells 51 itself would be made available with simultaneous impressions of voltage pulses 40 on all fuel cells 51 the situation that occurs in these during the application of the voltage pulses 40 there was a total failure or the performance of the fuel cells 51 would be significantly reduced. This would result in no or only a small electrical output from the fuel cells in these periods 51 could be made available. However, this would be the circuit arrangement 10 unable to receive the voltage pulses required for detoxification 40 to create. Through an appropriate selection or position of the switch element 56 can be achieved that the circuit arrangement 10 always from a fuel cell 51 or a fuel cell module is supplied with electrical energy that is not currently being subjected to voltage pulses, that is to say operates in normal operation.

The position of the switch element 56 is preferably coordinated with the position of the switch element 59 so that always such fuel cells 51 or fuel cell modules via the switch element 56 with the circuit arrangement 10 leading line 31 are connected, which are not currently on the switch element 59 with that of the circuit arrangement 10 laxative line 32 are connected.

10

circuitry

11

charging circuit

12

discharge circuit

13

capacity

14

load

20

switch arrangement

21

driving element

22

transistor

23

transistor

30

pulse generator

31

electrical Line (supply of electrical energy)

32

electrical Line (derivation of the voltage pulses)

33

circuit

34

circuit

35

switching element

36

counters block

37

Clock input

38

switching element

40

voltage pulse (rectangular)

50

The fuel cell system

51

fuel cell

52

Fuel / oxidizer supply line

53

Fuel / oxidizer discharge

54

battery

55

electrical connecting line

56

switching element

57

electrical connecting line

58

switching element

59

switching element

60

electrical connecting line

D

pulse duration

A

pulse interval

F

pulse rate

Claims (18)

Circuit arrangement for generating voltage pulses and for impressing the voltage pulses on a fuel cell, with a pulse generator ( 30 ) to generate the voltage pulses ( 40 ), one with the pulse generator ( 30 ) connected charging / discharging circuit ( 11 . 12 ), in which at least one fuel cell ( 51 ) and at least one capacity ( 13 ) is provided, and with a switch arrangement ( 20 ) for switching the charging / discharging circuit ( 11 . 12 ) in terms of capacity ( 13 ) during the voltage pulse impression in a charging circuit ( 11 ) and after the voltage pulse is impressed into a discharge circuit ( 12 ). Circuit arrangement according to claim 1, characterized in that in the discharge circuit ( 12 ) a burden ( 14 ) is provided. Circuit arrangement according to claim 2, characterized in that the load ( 14 ) as Lastwi the state and / or usable electrical consumers is formed. Circuit arrangement according to one of claims 1 to 3, characterized in that the capacitance ( 13 ) is designed as an UltraCap capacitor. Circuit arrangement according to one of claims 1 to 4, characterized in that the pulse generator ( 30 ) for the generation of essentially rectangular voltage pulses ( 40 ) is trained. Circuit arrangement according to claim 5, characterized in that the voltage pulses ( 40 ) have a variable pulse duration (D) and / or a variable pulse interval (A). Circuit arrangement according to one of claims 1 to 6, characterized in that the pulse generator ( 30 ) a circuit ( 33 ) for calibration of the pulse duration (D) of the voltage pulses ( 40 ) having. Circuit arrangement according to one of claims 1 to 7, characterized in that the pulse generator ( 30 ) a circuit ( 34 ) for variably setting the ratio of pulse duration (D) to pulse spacing (A) of the voltage pulses ( 40 ) having. Circuit arrangement according to claim 7 or 8, characterized in that the circuit ( 33 ) and / or the circuit ( 34 ) has one or more potentiometers. Circuit arrangement according to one of claims 7 to 9, characterized in that the pulse generator ( 30 ) one with the circuit ( 33 ) connected counter module ( 36 ) having. Circuit arrangement according to one of claims 8 to 10, characterized in that the pulse generator ( 30 ) a switch element ( 38 ) for switching between the circuit ( 33 ) and the circuit ( 34 ) having. Circuit arrangement according to one of claims 1 to 11, characterized in that the switch arrangement ( 20 ) a driver element ( 21 ) and one or more transistors ( 22 . 23 ) having. Circuit arrangement according to one of claims 1 to 12, characterized in that in the discharge circuit ( 12 an arrangement for smoothing the during the discharge of the capacity ( 13 ) about the load ( 14 ) provided electrical current is provided. Fuel cell system, with one or more fuel cells ( 51 ) and a circuit arrangement ( 10 ) according to one of claims 1 to 13, for generating voltage pulses ( 40 ) and for at least temporarily impressing the voltage pulses ( 40 ) on the fuel cell (s) ( 51 ). Fuel cell system according to claim 14, characterized in that the pulse generator ( 30 ) for reference to the generation of the voltage pulses ( 40 ) required electrical energy with one or more fuel cells ( 51 ) connected is. Fuel cell system according to claim 14 or 15, characterized in that the pulse generator ( 30 ) for reference to the generation of the voltage pulses ( 40 ) required electrical energy with a battery ( 54 ) connected is. Fuel cell system according to one of claims 14 to 16, characterized in that a plurality of fuel cell modules, each with a plurality of fuel cells ( 51 ) are provided. Fuel cell system according to claim 17, characterized in that the circuit arrangement ( 10 ) generated voltage pulses ( 40 ) can be stamped on each fuel cell module independently of other fuel cell modules.