DE102012016246A1 - Switching circuit for voltage source e.g. fuel cell stack, has semiconductor switch that generates conductive switching signal, when predetermined condition is not satisfied operation of voltage source - Google Patents

Abstract

The switching circuit (20) has a semiconductor switch (23) that is provided with power ports (31,32) and control terminal (50). The semiconductor switch is provided between power ports and is switched by signal generated from control circuit (24). The semiconductor switch generates conductive switching signal, when predetermined condition is not satisfied the operation of voltage source. An independent claim is included for a method for manufacturing low impedance end of voltage source.

Description

The invention relates to a circuit for producing a low-impedance termination of a voltage source according to the preamble of patent claim 1, a voltage source according to the preamble of patent claim 8, and to an operating method for producing a low-impedance termination of a voltage source according to the preamble of patent claim 9.

In the automotive industry, voltages> 60 V _{DC are} not permitted in switched-off systems and should therefore be prevented. The voltage must therefore be removed after the system has been switched off in due time. For this purpose, in components with charge storage, a proactive discharge is required, which must at least discharge the capacity installed in the respective system in due time. In a fuel cell system, under unfavorable circumstances, a voltage can build up that is reliably kept below 60 V when the system is not in operating mode (especially to avoid hazards during servicing).

From the WO 2009/052953 A1 is known to perform an emergency shutdown of a fuel cell stack (for example, in a dangerous situation) a short circuit and a discharge by means of a pyrotechnic switch.

Pyrotechnic switches have the disadvantage that they can only be ignited once and generally remain in a low-resistance state after ignition and that the voltage source (for example the fuel cell stack) can not then be put into operation again without workshop intervention.

It is therefore an object of the present invention, a circuit and an operating method of the type mentioned in such a way that the voltage source (for example, a fuel cell stack) can be put back into operation after an emergency shutdown without workshop intervention.

This object is achieved by a circuit having the features of patent claim 1, a voltage source having the features of patent claim 8 and by an operating method having the features of patent claim 9. Advantageous developments of the invention will become apparent from the dependent claims.

To realize a commissioning without workshop intervention after an emergency shutdown, it is provided in the circuit according to the invention that the circuit for producing a low-impedance termination of a voltage source having a first and a second supply terminal comprises a semiconductor switch and a control circuit, wherein the semiconductor switch has a first and a second Working terminal and at least one control terminal, wherein the semiconductor switch is prepared to be switched between the first and the second working port by means of a signal and the control circuit is prepared to generate the signal for Leitendschill the semiconductor switch, if at least one predetermined ambient condition for Operation of the voltage source is not fulfilled. The same applies to the voltage source, which comprises a circuit according to the invention for producing a low-impedance termination of the voltage source.

• – Überwachen einer Spannung einer Spannungsquelle;
• – Erzeugen eines Signals, sobald mindestens eine vorbestimmte Umgebungsbedingung zum Betrieb der Spannungsquelle nicht erfüllt ist; und
• – Kurzschließen der Spannungsquelle mittels eines auf Durchlass-Schaltens eines Halbleiterschalters.

Accordingly, the operating method according to the invention for producing a low-impedance termination of a voltage source comprises the following steps:

• - monitoring a voltage of a voltage source;
• - generating a signal as soon as at least one predetermined ambient condition for operation of the voltage source is not met; and
• - Short-circuiting of the voltage source by means of on-pass switching of a semiconductor switch.

The proposed measures a voltage at connection terminals of a voltage source can be guaranteed at any time when the power source is in non-operating mode. This is particularly advantageous if the voltage source is a removed fuel cell stack.

It is preferred that a predetermined ambient condition for operation of the voltage source is considered not satisfied if a terminal voltage is exceeded in the absence of an external signal at the control terminal.

Optionally, the circuit may be prepared to switch the semiconductor switch passively or by a signal to non-passing once predetermined environmental conditions for operating the voltage source are met. In addition, the discharge is reversible in case of danger. This means that the user can restart the voltage source with the safety circuit (discharge circuit and / or low-impedance termination) after a danger shutdown without the intervention of the garage, if the high-voltage system is still intact. The discharge device can also be used in voltage networks in order to prevent overcharging devices of individual high-voltage components that are designed too weakly being overloaded due to an excessively high residual charge in the voltage network. If the semiconductor switch is a thyristor that can be rendered non-conductive only by dropping its holding current and if the voltage source is a fuel cell, then the thyristor can not be turned off by removing at least one of the reactants from the fuel cell.

It is also expedient if the control circuit comprises a tripping device that is prepared to directly or indirectly generate a signal for conducting the semiconductor switch when a voltage between the first and the second working connection exceeds a predetermined voltage limit.

It is also preferred if the control circuit comprises a diagnostic device which is prepared to monitor a functionality of a voltage monitor, a gate driver, a triggering circuit, a current through the semiconductor switch, a functionality of the semiconductor switch and / or a property of the semiconductor switch. The circuit can be used to switch a fuel cell stack in the event of an accident by means of short-circuiting and discharging voltage. When using a reversible instead of an irreversible semiconductor switch (short-circuit element), a build-up of stress at rest can be prevented.

A particularly preferred embodiment provides that the control circuit comprises a gate driver, which is prepared to switch the semiconductor switch on the instruction of the trigger circuit on passage.

In addition, the control circuit may comprise a potential-free balanced or unbalanced control terminal, which is prepared to deactivate generation of the signal to turn off the semiconductor switch upon application of a deactivation signal to the control terminal in the control circuit.

It can be advantageous if the operating method also includes a step in which the semiconductor switch is switched to non-passage as soon as predetermined environmental conditions are met.

The present invention will now be explained in more detail with reference to the accompanying drawing, which shows a schematic structure of a circuit according to the invention.

The figure shows a voltage source 10 and a circuit 20 for safety shutdown of the voltage source 10 , The voltage source 10 includes a first 12 and a second 12 Supply connection. The circuit 20 includes a semiconductor switch 23 and a control circuit 24 , The semiconductor switch 23 has a first 31 and a second 32 Working connection and at least one control connection 33 on. The semiconductor switch 23 can be between the first 31 and the second 32 Working connection to be switched by means of a signal conductive. The control circuit 24 the signal can be used to turn on the semiconductor switch 23 generate when a predetermined environmental condition for operation of the voltage source 10 is not fulfilled. The circuit 20 can the semiconductor switch 23 passively or by means of a signal switch to non-passage as soon as predetermined environmental conditions for operation of the voltage source 10 are fulfilled.

The control circuit 24 can be a triggering device 26 have, which is intended to directly or indirectly a signal for Leitendschalten the semiconductor switch 23 to generate when a voltage U between the first 31 and the second 32 Work connection exceeds a predetermined voltage limit. Preferably, the control circuit causes 24 (automatically or self-activating) a Leitendschalten the semiconductor switch 23 when at the control terminal 50 no external signal is present. By applying an external signal to the control terminal 50 becomes the self-activity of the control circuit 23 canceled. This state is referred to here as 'disabled' or 'disabled'. As long as the external signal is present, the voltage source can 20 operated as intended. As soon as the external signal is missing, the control circuit 24 again self-active and ensures the intended absence of voltage (for example for U less than 50 V).

The power supply unit 42 serves to cut off the voltage between the high-voltage terminals 21 . 22 the unloading device 20 is applied, a voltage to supply the gate driver 44 and the triggering device 26 derive and provide. Voltages above 60 V are often referred to as high voltage (HV) in the automotive sector. The control circuit 24 can be a diagnostic device 28 have a functionality of voltage monitoring 42 , a gate driver 44 and a triggering device 26 supervised. The control circuit 24 can be a gate driver 44 comprising the semiconductor switch 23 upon instruction of the tripping device 26 switched to passage.

The control circuit 24 can be a potential-free, balanced or unbalanced control connection 50 exhibit. The control connection 50 may be prepared to provide control signals from and / or to the control circuit 24 to convey. In addition, the control port 50 be prepared to the control circuit 24 electrical To supply energy. The low voltage supply unit 52 (For example, a converter) is used for galvanic isolation of the control terminal 50 from remaining parts of the control circuit 24 and the power supply of the diagnostic device 28 ,

The exemplary embodiment has the following functional properties: Without signal at the control connection 50 the unloading function is active. Ie. at voltage increase between the high-voltage connections 21 . 22 About (about 50 V) is the thyristor 23 ignited. This remains conductive until the current between the high-voltage terminals 21 . 22 the holding current of the thyristor 23 below. The power supply unit 42 generates a well-defined voltage to monitor the high voltage U and to trigger the thyristor 23 , The gate driver 44 ensures a sufficient ignition current of the thyristor 23 , The triggering device 26 monitors the voltage U between the high-voltage terminals 21 . 22 and triggers the gate driver 44 when a threshold voltage is exceeded.

The diagnostic device 28 has the task of the functionality of the diagnostic switch S1, the gate driver 44 and the triggering device 26 to monitor. With normal functionality, the switch S2 (for example, a phototransistor) will become the diagnostic device 28 closed periodically. This can be evaluated by an evaluating unit as 'Gutsignal'. Because in case of malfunction, the switch S2 remains open. Alternatively or additionally, it is also possible that the diagnostic device 28 the control terminal 50 Relieved by switching off a load resistor, so that via the control terminal 50 drawn current drops significantly and this can be detected by a controlling device.

Is located at the control terminal 50 a predetermined signal for this, the discharge function by means of opening the switch S1, which is normally closed, reliably deactivated. At the same time, a defined current through the low voltage supply unit 52 a diagnostic signal, which has the meaning 'component OK', for example.

• – Schnellentladung zur Sicherstellung einer Spannungsfreiheit bei gleichzeitiger Verfügbarkeit nach einer Notabschaltung;
• – Verhinderung eines Wiederaufbaus der Spannung (bei Brennstoffzellen grundsätzlich denkbar);
• – Start des Brennstoffzellenstapels gegen einen niederohmigen Abschluss (bei sehr tiefen Temperaturen ist eine schnelle Erwärmung des Brennstoffzellenstapels möglich; sogenannter ”Freeze Start-up”; ein ”Freeze Start-up” kann beendet werden, sobald der Brennstoffzellenstapel eine vorbestimmte Temperatur erreicht hat oder einen vorbestimmten Strom liefert. Der Strom durch den Thyristor kann beispielsweise mittelbar anhand einer Erwärmung des Thyristors oder anhand einer Messung eines Spannungsabfalls überwacht werden.);
• – zentrale Entladeeinheit innerhalb eines Hochvoltsystems, Absicherung gegen einen unbeabsichtigten Spannungsaufbau (beispielsweise über 12 V/400 V DC-DC-Wandler für 100 mW);
• – niederohmiger Abschluss eines Quellensystems, welches nicht vollständig galvanisch getrennt werden kann (beispielsweise bei Batteriesystem mit Halbleiterschalter zur Trennung); und
• – Notabschaltung einer Quelle/Batterie, die (evtl. nur) durch eine Schmelzsicherung gesichert ist.

The present invention can be used, for example, for the following applications:

• - Fast discharge to ensure a voltage-free with simultaneous availability after an emergency shutdown;
• - Preventing a rebuilding of the voltage (in fuel cells in principle conceivable);
• - Start of the fuel cell stack against a low-impedance termination (at very low temperatures a rapid warming of the fuel cell stack is possible, so-called "freeze start-up", a "freeze start-up" can be terminated as soon as the fuel cell stack has reached a predetermined temperature or a For example, the current through the thyristor may be indirectly monitored by heating the thyristor or by measuring a voltage drop.);
• - Central discharge unit within a high-voltage system, protection against unintentional voltage build-up (for example, over 12 V / 400 V DC-DC converter for 100 mW);
• Low-resistance termination of a source system, which can not be completely galvanically isolated (for example, in battery system with semiconductor switch for separation); and
• - emergency shutdown of a source / battery, which is (possibly only) secured by a fuse.

The semiconductor switch 23 may have the property of being able to switch reversibly high currents of, for example, about 3 to 5 kA in the case of a low-resistance resistance or a small voltage drop (<10 V). For example, thyristors, IGBT, MOSFET, spark gaps are suitable for this purpose.

Typically, the unloading device comprises two high-voltage terminals 21 . 22 and a floating balanced or unbalanced control terminal 50 ,

• – Selbstaktivierung ohne Fremdversorgung bei Anstieg über eine kritische Spannung (beispielsweise über 60 V);
• – einen galvanisch getrennten Steueranschluss 50 zur Deaktivierung der Selbstaktivierung, vorzugsweise in 2-Leitertechnik (bei Redundanz in 4-Leitertechnik);
• – Selbstdiagnose und Kommunikation über den galvanisch getrennten Steueranschluss 50, ggf. über eine Steuerleitung;
• – Zur Deaktivierung eines durchgeschalteten Thyristors gibt es folgende Möglichkeiten:
• – Es kann ein GTO-Thyristor (Gate-Turn-Off-Thyristor) verwendet werden.
• – Wenn der Halbleiterschalter ein Thyristor ist, der nur durch Unterschreiten des Haltestroms nichtleitend geschaltet werden kann und wenn die Spannungsquelle eine Brennstoffzelle ist, dann kann das Nicht-Leitendschalten des Thyristors auch durch Fernhalten mindestens eines der Reaktanten (Reaktionsedukte) von der Brennstoffzelle bewirkt werden. Der Abfall des Stroms unter den Haltestrom des Thyristors kann beschleunigt werden, indem ein Thyristor mit einem hohen Haltestrom verwendet wird (allerdings ist ein hoher Haltestrom üblicherweise eine unerwünschte Eigenschaft von Thyristoren).
• – Anstelle eines GTO-Thyristors oder eines Thyristors mit einem hohen Haltestrom kann auch ein konventioneller Thyristor parallel zu einem MOS-FET verwendet werden. Zur Deaktivierung des Thyristors kann der MOSFET den Thyristor bei kleineren bis mittleren Strömen den Thyristor in den nichtleitenden Zustand versetzen, indem er die Arbeitsanschlüsse des Thyristors kurzschließt. Dies kann beispielsweise zur Freigabe des Thyristors nach einem Kaltstart (Betrieb des Brennstoffzellenstapels gegen einen niederohmigen Abschluss) zur Anwendung kommen.

Optionally, the control circuit 24 also have one or more of the following characteristics:

• - self-activation without external supply when rising above a critical voltage (for example above 60 V);
• - a galvanically isolated control connection 50 for deactivation of self-activation, preferably in 2-wire technology (with redundancy in 4-wire technology);
• - Self-diagnosis and communication via the galvanically isolated control connection 50 , if necessary via a control line;
• - To deactivate a thyristor switched through, there are the following options:
• - A GTO thyristor (gate turn-off thyristor) can be used.
• If the semiconductor switch is a thyristor which can be made non-conductive only by dropping the holding current and if the voltage source is a fuel cell, then the thyristor can not be turned off by keeping at least one of the reactants (reaction educts) from the fuel cell. The drop in current below the holding current of the thyristor can be accelerated by using a high holding current thyristor (however, a high Holding current usually an undesirable feature of thyristors).
• - Instead of a GTO thyristor or a thyristor with a high holding current and a conventional thyristor can be used in parallel to a MOS-FET. To deactivate the thyristor, the MOSFET can put the thyristor in the non-conducting state at low to medium currents by short-circuiting the working terminals of the thyristor. This can be used, for example, to enable the thyristor after a cold start (operation of the fuel cell stack against a low-impedance termination).

LIST OF REFERENCE NUMBERS

10

voltage source

11

first supply connection

12

second supply connection,

20

Circuit; discharge

21

first high-voltage connection of the unloading device

22

second high-voltage connection of the unloading device

23

Semiconductor switches

24

control circuit

26

triggering device

28

diagnostic device

31

first work connection

32

second work connection

33

control connection

42

Power supply unit

44

gate drivers

50

control connection

52

Low-voltage supply unit

U

Voltage between supply connections

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2009/052953 A1 [0003]

Claims (10)

Circuit ( 20 ) for producing a low-impedance termination of a voltage source ( 10 ) with a first ( 11 ) and a second ( 12 ) Supply connection, characterized in that the circuit ( 20 ) a semiconductor switch ( 23 ) and a control circuit ( 24 ), wherein the semiconductor switch ( 23 ) a first ( 31 ) and a second ( 32 ) Working connection and at least one control connection ( 50 ), wherein the semiconductor switch ( 23 ) is prepared to work between the first ( 31 ) and the second ( 32 ) Working connection by means of a signal to be turned on and the control circuit ( 24 ) is prepared, the signal for Leitendschalten the semiconductor switch ( 23 ) if at least one predetermined environmental condition for operation of the voltage source ( 10 ) is not fulfilled. Circuit according to Claim 1, characterized in that a predetermined ambient condition for operation of the voltage source ( 10 ) is not satisfied if, in the absence of an external signal at the control connection ( 50 ) a terminal voltage is exceeded. Circuit according to Claim 1 or 2, characterized in that the circuit ( 24 ) is prepared, the semiconductor switch ( 23 ) passively or by means of a signal to non-passage, as soon as predetermined environmental conditions for operation of the voltage source ( 10 ) are met. Circuit according to one of Claims 1 to 3, characterized in that the control circuit ( 24 ) a triggering device ( 26 ), which is prepared to directly or indirectly supply a signal for conducting the semiconductor switch ( 23 ), when a voltage (U) between the first and the second working connection ( 31 . 32 ) exceeds a predetermined voltage limit. Circuit ( 20 ) according to one of claims 1 to 4, characterized in that the control circuit ( 24 ) a diagnostic device ( 28 ), which is prepared to perform a functionality of voltage monitoring ( 42 ), a gate driver ( 44 ), a triggering device ( 26 ), a current through the semiconductor switch ( 23 ), a functionality of the semiconductor switch ( 23 ) and / or a property of the semiconductor switch ( 23 ). Circuit ( 20 ) according to one of claims 1 to 5, characterized in that the control circuit ( 24 ) a gate driver ( 44 ), which is ready to use the semiconductor switch ( 23 ) on instruction of the triggering device ( 26 ) switch to passage. Circuit ( 20 ) according to one of claims 1 to 6, characterized in that the control circuit ( 24 ) a floating symmetric or unbalanced control terminal ( 50 ) prepared to respond to a deactivation signal at the control port ( 50 ) in the control circuit ( 24 ) a generation of the signal for Leitendschalten the semiconductor switch ( 23 ). Voltage source ( 10 ), in particular fuel cell stack, characterized in that the voltage source ( 10 ) a circuit ( 20 ) according to any one of claims 1 to 7. Operating method for producing a low-impedance termination of a voltage source ( 10 ), characterized in that the operating method comprises the following steps: - monitoring a voltage (U) of a voltage source ( 10 ); Generating a signal as soon as at least one predetermined ambient condition for operation of the voltage source ( 10 ) is not fulfilled; and - short-circuiting the voltage source ( 10 ) by means of on-pass switching of a semiconductor switch ( 23 ). Operating method according to claim 9, characterized in that the operating method also comprises the following step: - on non-forward switching of the semiconductor switch ( 23 ) as soon as predetermined environmental conditions are met.

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